548 lines
18 KiB
Markdown
548 lines
18 KiB
Markdown
# 使用 kubebuilder 创建 operator 示例
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本文作为 Kubebuilder 教程，将指导您如何使用 kubebuilder 创建一个 Kubernetes Operator。
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## 准备
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本文中的示例运行环境及相关软件版本如下：
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- Kubernetes MiniKube v1.9.2
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- Kubernetes v1.18.0
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- Go 1.14
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- Kubebuilder 2.3.1
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- kustomize 3.6.1
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- Docker 19.03.8
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使用 Minikube 安装 Kubernetes 集群，Kubernetes 安装好后，检查集群是否可用。
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### Minikube 的 DNS 解析问题
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如果遇到 Kubernetes 集群无法拉取镜像，DNS 解析出现问题，解决方式见 [DNS lookup not working when starting minikube with --dns-domain #1674](https://github.com/kubernetes/minikube/issues/1674)。
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使用 `minikube ssh` 进入 minikube 主机，修改 `/etc/systemd/resolved.conf` 文件，将其中的 DNS 配置字段修改为 `DNS=8.8.8.8`，然后执行 `sudo systemctl restart systemd-resolved` 即可更改 DNS，切勿直接修改 `/etc/resolv.conf` 文件。
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修正 Minikube 的 DNS 配置，请执行下面的命令。
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```bash
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minikube ssh
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sudo sed -i 's/#DNS=/DNS=8.8.8.8/g' /etc/systemd/resolved.conf
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sudo systemctl restart systemd-resolved
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```
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## 名词解释
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在阅读下面的文章前，需要先明确以下两个名词的含义。
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- CRD：自定义资源定义，Kubernetes 中的资源类型。
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- CR：Custom Resource，对使用 CRD 创建出来的自定义资源的统称。
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## 安装 kubebuilder
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到 kubebuilder 的 [GitHub release 页面](https://github.com/kubernetes-sigs/kubebuilder/releases)上下载与您操作系统对应的 kubebuilder 安装包。
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**MacOS**
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对于 Mac 系统，将下载好的安装包解压后将其移动到 `/usr/local/kubebuilder` 目录下，并将 `/usr/local/kubebuilder/bin` 添加到您的 `$PATH` 路径下。
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## 创建项目
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我们首先将使用自动配置创建一个项目，该项目在创建 CR 时不会触发任何资源生成。
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### 初始化和创建 API
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创建的项目路径位于 `$GOPATH/jimmysong.io/kubebuilder-example`。下文中的操作没有明确说明的话都是在该项目路径下运行。
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在项目路径下使用下面的命令初始化项目。
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```bash
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$ kubebuilder init --domain jimmysong.io
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```
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在项目根目录下执行下面的命令创建 API。
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```bash
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$ kubebuilder create api --group webapp --version v1 --kind Guestbook
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Create Resource under pkg/apis [y/n]?
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y
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Create Controller under pkg/controller [y/n]?
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y
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Writing scaffold for you to edit...
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api/v1/guestbook_types.go
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controllers/guestbook_controller.go
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Running make:
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$ make
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/Users/jimmysong/Workspace/go/bin/controller-gen object:headerFile="hack/boilerplate.go.txt" paths="./..."
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go fmt ./...
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go vet ./...
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go: finding github.com/onsi/ginkgo v1.11.0
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go: finding github.com/onsi/gomega v1.8.1
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go: finding github.com/hpcloud/tail v1.0.0
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go: finding gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7
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go build -o bin/manager main.go
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```
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API 创建完成后，在项目根目录下查看目录结构。
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```bash
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.
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├── Dockerfile # 用于构建 Operator 镜像
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├── Makefile # 构建时使用
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├── PROJECT # 项目配置
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├── api
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│ └── v1
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│ ├── groupversion_info.go
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│ ├── guestbook_types.go
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│ └── zz_generated.deepcopy.go
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├── bin
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│ └── manager
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├── config
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│ ├── certmanager
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│ │ ├── certificate.yaml
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│ │ ├── kustomization.yaml
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│ │ └── kustomizeconfig.yaml
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│ ├── crd # 新增 CRD 定义
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│ │ ├── kustomization.yaml
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│ │ ├── kustomizeconfig.yaml
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│ │ └── patches
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│ ├── default
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│ │ ├── kustomization.yaml
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│ │ ├── manager_auth_proxy_patch.yaml
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│ │ ├── manager_webhook_patch.yaml
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│ │ └── webhookcainjection_patch.yaml
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│ ├── manager
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│ │ ├── kustomization.yaml
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│ │ └── manager.yaml
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│ ├── prometheus
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│ │ ├── kustomization.yaml
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│ │ └── monitor.yaml
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│ ├── rbac
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│ │ ├── auth_proxy_client_clusterrole.yaml
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│ │ ├── auth_proxy_role.yaml
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│ │ ├── auth_proxy_role_binding.yaml
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│ │ ├── auth_proxy_service.yaml
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│ │ ├── guestbook_editor_role.yaml
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│ │ ├── guestbook_viewer_role.yaml
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│ │ ├── kustomization.yaml
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│ │ ├── leader_election_role.yaml
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│ │ ├── leader_election_role_binding.yaml
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│ │ └── role_binding.yaml
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│ ├── samples
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│ │ └── webapp_v1_guestbook.yaml # CRD 示例
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│ └── webhook
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│ ├── kustomization.yaml
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│ ├── kustomizeconfig.yaml
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│ └── service.yaml
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├── controllers # 新增 controller
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│ ├── guestbook_controller.go
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│ └── suite_test.go
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├── go.mod
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├── go.sum
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├── hack
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│ └── boilerplate.go.txt
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└── main.go # 新增处理逻辑
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15 directories, 40 files
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```
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以上就是自动初始化出来的文件。
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### 安装 CRD
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执行下面的命令安装 CRD。
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```bash
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$ make install
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/Users/jimmysong/Workspace/go/bin/controller-gen "crd:trivialVersions=true" rbac:roleName=manager-role webhook paths="./..." output:crd:artifacts:config=config/crd/bases
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kustomize build config/crd | kubectl apply -f -
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customresourcedefinition.apiextensions.k8s.io/guestbooks.webapp.jimmysong.io created
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$ kubectl get crd |grep jimmysong.io
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guestbooks.webapp.jimmysong.io 2020-06-06T21:58:17Z
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```
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### 部署 controller
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在开始部署 controller 之前，我们需要先检查 kubebuilder 自动生成的 YAML 文件。
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**修改使用 gcr.io 镜像仓库的镜像地址**
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对于中国大陆用户，可能无法访问 Google 镜像仓库 gcr.io，因此需要修改 `config/default/manager_auth_proxy_patch.yaml` 文件中的镜像地址，将其中 `gcr.io/kube-rbac-proxy:v0.5.0` 修改为 `jimmysong/kubebuilder-kube-rbac-proxy:v0.5.0`。
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有两种方式运行 controller：
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- 本地运行，用于调试
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- 部署到 Kubernetes 上运行，作为生产使用
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**本地运行 controller**
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要想在本地运行 controller，只需要执行下面的命令。
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```bash
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make run
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```
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你将看到 controller 启动和运行时输出。
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**将 controller 部署到 Kubernetes**
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执行下面的命令部署 controller 到 Kubernetes 上，这一步将会在本地构建 controller 的镜像，并推送到 DockerHub 上，然后在 Kubernetes 上部署 Deployment 资源。
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```bash
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make docker-build docker-push IMG=jimmysong/kubebuilder-example:latest
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make deploy IMG=jimmysong/kubebuilder-example:latest
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```
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在初始化项目时，kubebuilder 会自动根据项目名称创建一个 Namespace，如本文中的 `kubebuilder-example-system`，查看 Deployment 对象和 Pod 资源。
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```bash
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$ kubectl get deployment -n kubebuilder-example-system
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NAME READY UP-TO-DATE AVAILABLE AGE
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kubebuilder-example-controller-manager 1/1 1 1 3h26m
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$ kubectl get pod -n kubebuilder-example-system
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NAME READY STATUS RESTARTS AGE
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kubebuilder-example-controller-manager-77b4c685f9-2npz8 2/2 Running 0 3h16m
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```
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### 创建 CR
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Kubebuilder 在初始化项目的时候已生成了示例 CR，执行下面的命令部署 CR。
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```bash
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kubectl apply -f config/samples/webapp_v1_guestbook.yaml
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```
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执行下面的命令查看新创建的 CR。
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```bash
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$ kubectl get guestbooks.webapp.jimmysong.io guestbook-sample -o yaml
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```
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你将看到类似如下的输出。
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```yaml
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apiVersion: webapp.jimmysong.io/v1
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kind: Guestbook
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metadata:
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annotations:
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kubectl.kubernetes.io/last-applied-configuration: |
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{"apiVersion":"webapp.jimmysong.io/v1","kind":"Guestbook","metadata":{"annotations":{},"name":"guestbook-sample","namespace":"kubebuilder-example-system"},"spec":{"foo":"bar"}}
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creationTimestamp: "2020-06-07T01:04:48Z"
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generation: 1
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managedFields:
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- apiVersion: webapp.jimmysong.io/v1
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fieldsType: FieldsV1
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fieldsV1:
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f:metadata:
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f:annotations:
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.: {}
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f:kubectl.kubernetes.io/last-applied-configuration: {}
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f:spec:
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.: {}
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f:foo: {}
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manager: kubectl
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operation: Update
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time: "2020-06-07T01:04:48Z"
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name: guestbook-sample
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namespace: kubebuilder-example-system
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resourceVersion: "1795834"
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selfLink: /apis/webapp.jimmysong.io/v1/namespaces/kubebuilder-example-system/guestbooks/guestbook-sample
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uid: 051a4266-7f5a-4c57-8180-64222d462bba
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spec:
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foo: bar
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```
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至此一个基本的 Operator 框架已经创建完成，但这个 Operator 只是修改了 etcd 中的数据而已，实际上什么事情也没做，因为我们没有在 Operator 中的增加业务逻辑。
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## 增加业务逻辑
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下面我们将修改 CRD 的数据结构并在 controller 中增加一些日志输出。
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### 修改 CRD
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我们将修改上文中使用 kubebuilder 命令生成的默认 CRD 配置，在 CRD 中增加 `FirstName`、`LastName` 和 `Status` 字段。
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下面是修改后的 `api/v1/guestbook_types.go` 文件的内容，对应修改的地方已在代码中注释说明。
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```go
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/*
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package v1
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import (
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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)
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// EDIT THIS FILE! THIS IS SCAFFOLDING FOR YOU TO OWN!
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// NOTE: json tags are required. Any new fields you add must have json tags for the fields to be serialized.
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// GuestbookSpec defines the desired state of Guestbook
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type GuestbookSpec struct {
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// INSERT ADDITIONAL SPEC FIELDS - desired state of cluster
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// Important: Run "make" to regenerate code after modifying this file
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// Foo is an example field of Guestbook. Edit Guestbook_types.go to remove/update
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// 添加两个新的字段
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FirstName string `json:"firstname"`
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LastName string `json:"lastname"`
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}
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// GuestbookStatus defines the observed state of Guestbook
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type GuestbookStatus struct {
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// INSERT ADDITIONAL STATUS FIELD - define observed state of cluster
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// Important: Run "make" to regenerate code after modifying this file
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Status string `json:"Status"`
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}
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// +kubebuilder:object:root=true
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// 在这里增加 status 的说明
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// +kubebuilder:subresource:status
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// Guestbook is the Schema for the guestbooks API
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type Guestbook struct {
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metav1.TypeMeta `json:",inline"`
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metav1.ObjectMeta `json:"metadata,omitempty"`
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Spec GuestbookSpec `json:"spec,omitempty"`
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Status GuestbookStatus `json:"status,omitempty"`
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}
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// +kubebuilder:object:root=true
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// GuestbookList contains a list of Guestbook
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type GuestbookList struct {
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metav1.TypeMeta `json:",inline"`
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metav1.ListMeta `json:"metadata,omitempty"`
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Items []Guestbook `json:"items"`
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}
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func init() {
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SchemeBuilder.Register(&Guestbook{}, &GuestbookList{})
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}
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```
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上面的代码比原先使用 kubebuilder 生成的默认代码增加了以下内容：
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```go
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FirstName string `json:"firstname"`
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LastName string `json:"lastname"`
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Status string `json:"Status"`
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// +kubebuilder:subresource:status
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```
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### 修改 Reconcile 函数
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Reconcile 函数是 Operator 的核心逻辑，Operator 的业务逻辑都位于 `controllers/guestbook_controller.go` 文件的 `func (r *GuestbookReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error)` 函数中。
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```go
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// +kubebuilder:rbac:groups=webapp.jimmysong.io,resources=guestbooks,verbs=get;list;watch;create;update;patch;delete
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// +kubebuilder:rbac:groups=webapp.jimmysong.io,resources=guestbooks/status,verbs=get;update;patch
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func (r *GuestbookReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
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_ = context.Background()
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_ = r.Log.WithValues("guestbook", req.NamespacedName)
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// your logic here
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ctx := context.Background()
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_ = r.Log.WithValues("apiexamplea", req.NamespacedName)
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// 获取当前的 CR，并打印
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obj := &webappv1.Guestbook{}
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if err := r.Get(ctx, req.NamespacedName, obj); err != nil {
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log.Println(err, "Unable to fetch object")
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} else {
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log.Println("Geeting from Kubebuilder to", obj.Spec.FirstName, obj.Spec.LastName)
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}
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// 初始化 CR 的 Status 为 Running
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obj.Status.Status = "Running"
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if err := r.Status().Update(ctx, obj); err != nil {
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log.Println(err, "unable to update status")
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}
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return ctrl.Result{}, nil
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}
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```
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这段代码的业务逻辑是当发现有 `guestbooks.webapp.jimmysong.io` 的 CR 变更时，在控制台中输出日志。
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### 运行测试
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修改好 Operator 的业务逻辑后，再测试一下新的逻辑是否可以正常运行。
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**部署 CRD**
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跟上文的做法一样，执行下面的命令部署 CRD。
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```bash
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make install
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```
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**运行 controller**
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跟上文的做法一样，执行下面的命令运行 controller。为了方便起见，我们将在本地运行 controller，当然您也可以将其部署到 Kubernetes 上运行。
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```bash
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make run
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```
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保持该窗口在前台运行。
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**部署 CR**
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修改 `config/samples/webapp_v1_guestbook.yaml` 文件中的配置。
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```yaml
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apiVersion: webapp.jimmysong.io/v1
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kind: Guestbook
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metadata:
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name: guestbook-sample
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spec:
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# Add fields here
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firstname: Jimmy
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lastname: Song
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```
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将其应用到 Kubernetes。
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```bash
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kubectl apply -f config/samples/webapp_v1_guestbook.yaml
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```
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此时转到上文中运行 controller 的窗口，将在命令行前台中看到如下输出。
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```bash
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go fmt ./...
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go vet ./...
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/Users/jimmysong/Workspace/go/bin/controller-gen "crd:trivialVersions=true" rbac:roleName=manager-role webhook paths="./..." output:crd:artifacts:config=config/crd/bases
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go run ./main.go
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2020-06-07T16:48:29.966+0800 INFO controller-runtime.metrics metrics server is starting to listen {"addr": ":8080"}
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2020-06-07T16:48:29.967+0800 INFO setup starting manager
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2020-06-07T16:48:29.967+0800 INFO controller-runtime.manager starting metrics server {"path": "/metrics"}
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2020-06-07T16:48:29.967+0800 INFO controller-runtime.controller Starting EventSource {"controller": "guestbook", "source": "kind source: /, Kind="}
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2020-06-07T16:48:30.068+0800 INFO controller-runtime.controller Starting Controller {"controller": "guestbook"}
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2020-06-07T16:48:30.068+0800 INFO controller-runtime.controller Starting workers {"controller": "guestbook", "worker count": 1}
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2020/06/07 16:48:30 Geeting from Kubebuilder to Jimmy Song
|
||
2020-06-07T16:48:30.080+0800 DEBUG controller-runtime.controller Successfully Reconciled {"controller": "guestbook", "request": "kubebuilder-example-system/guestbook-sample"}
|
||
```
|
||
|
||
从上面的日志中，可以看到这条输出。
|
||
|
||
```bash
|
||
2020/06/07 16:48:30 Geeting from Kubebuilder to Jimmy Song
|
||
```
|
||
|
||
这正是在 `Reconcile` 函数中的输出。
|
||
|
||
**获取当前的 CR**
|
||
|
||
使用下面的命令获取当前的 CR。
|
||
|
||
```bash
|
||
# kubectl get guestbooks.webapp.jimmysong.io guestbook-sample -o yaml
|
||
```
|
||
|
||
将看到如下输出。
|
||
|
||
```yaml
|
||
apiVersion: webapp.jimmysong.io/v1
|
||
kind: Guestbook
|
||
metadata:
|
||
annotations:
|
||
kubectl.kubernetes.io/last-applied-configuration: |
|
||
{"apiVersion":"webapp.jimmysong.io/v1","kind":"Guestbook","metadata":{"annotations":{},"name":"guestbook-sample","namespace":"kubebuilder-example-system"},"spec":{"firstname":"Jimmy","lastname":"Song"}}
|
||
creationTimestamp: "2020-06-07T02:54:46Z"
|
||
generation: 1
|
||
managedFields:
|
||
- apiVersion: webapp.jimmysong.io/v1
|
||
fieldsType: FieldsV1
|
||
fieldsV1:
|
||
f:metadata:
|
||
f:annotations:
|
||
.: {}
|
||
f:kubectl.kubernetes.io/last-applied-configuration: {}
|
||
f:spec:
|
||
.: {}
|
||
f:firstname: {}
|
||
f:lastname: {}
|
||
manager: kubectl
|
||
operation: Update
|
||
time: "2020-06-07T02:54:46Z"
|
||
- apiVersion: webapp.jimmysong.io/v1
|
||
fieldsType: FieldsV1
|
||
fieldsV1:
|
||
f:status:
|
||
.: {}
|
||
f:Status: {}
|
||
manager: main
|
||
operation: Update
|
||
time: "2020-06-07T02:56:38Z"
|
||
name: guestbook-sample
|
||
namespace: kubebuilder-example-system
|
||
resourceVersion: "1813769"
|
||
selfLink: /apis/webapp.jimmysong.io/v1/namespaces/kubebuilder-example-system/guestbooks/guestbook-sample
|
||
uid: 17da5eae-1020-40d2-821a-9a1f990dd767
|
||
spec:
|
||
firstname: Jimmy
|
||
lastname: Song
|
||
status:
|
||
Status: Running
|
||
```
|
||
|
||
我们输出的最后部分：
|
||
|
||
```yaml
|
||
spec:
|
||
firstname: Jimmy
|
||
lastname: Song
|
||
status:
|
||
Status: Running
|
||
```
|
||
|
||
这正是我们在 CRD 里定义的字段。
|
||
|
||
**删除 CR**
|
||
|
||
使用下面的命令删除 CR。
|
||
|
||
```bash
|
||
kubectl delete guestbooks.webapp.jimmysong.io guestbook-sample
|
||
```
|
||
|
||
此时在 controller 的前台输出中可以看到以下内容。
|
||
|
||
```bash
|
||
2020/06/07 20:09:50 Guestbook.webapp.jimmysong.io "guestbook-sample" not found Unable to fetch object
|
||
2020/06/07 20:09:50 resource name may not be empty unable to update status
|
||
2020-06-07T20:09:50.380+0800 DEBUG controller-runtime.controller Successfully Reconciled {"controller": "guestbook", "request": "kubebuilder-example-system/guestbook-sample"}
|
||
```
|
||
|
||
因为该 CR 被删除，因此日志中会提示资源找不到。
|
||
|
||
## 更多
|
||
|
||
本示例仅展示了使用 kubebuilder 创建 Operator 的基本逻辑，步骤为：
|
||
|
||
- 初始化项目和 API
|
||
- 安装 CRD
|
||
- 部署 Controller
|
||
- 创建 CR
|
||
|
||
Operator 的核心逻辑都在 controller 的 `Reconcile` 函数中，请参考 [Awesome Cloud Native](https://jimmysong.io/awesome-cloud-native/#kubernetes-operators) 中的 Operator 实现，本书后续将会讨论。
|
||
|
||
## 参考
|
||
|
||
- [如何使用 KubeBuilder 开发一个 Operator - chenshaowen.com](https://chenshaowen.com/blog/how-to-develop-a-operator-using-kubebuilder.html)
|
||
- [Kubebuilder book - kubebuilder.io](https://kubebuilder.io/quick-start.html) |