k8s之CRD--為自定義資源生成代碼

simon_chen 發(fā)布于2019-07-01 16:41 / 728人閱讀

摘要：看過的應(yīng)該都知道項(xiàng)目中有大量代碼工具生成的代碼。執(zhí)行即腳本將自動(dòng)生成下面的文件和路徑腳本運(yùn)行后大體會(huì)建立如下的包管理結(jié)構(gòu)是不是很簡(jiǎn)單代碼是被完全生成的，就像包含我們的語言類型的文件下面的文件一樣然后你就可以基于生成的代碼寫自己的了。

CRD簡(jiǎn)介和使用姿勢(shì)

CustomResourceDefinition（CRD）是 v1.7 + 新增的無需改變代碼就可以擴(kuò)展 Kubernetes API 的機(jī)制，用來管理自定義對(duì)象。它實(shí)際上是 ThirdPartyResources（TPR）的升級(jí)版本，而 TPR 已經(jīng)在 v1.8 中刪除。

一些使用場(chǎng)景：

提供/管理外部數(shù)據(jù)存儲(chǔ)/數(shù)據(jù)庫(例如 CloudSQL/RDS 實(shí)例)

對(duì)k8s基礎(chǔ)資源進(jìn)行更高層次的抽象(比如定義一個(gè)etcd集群)

其實(shí)crd在很多k8s周邊開源項(xiàng)目中有使用，比如ingress-controller和眾多的operator。

CRD 控制器

在使用 CRD 擴(kuò)展 Kubernetes API 時(shí)，通常還需要實(shí)現(xiàn)一個(gè)新建資源的控制器，監(jiān)聽改資源的變化情況，并作進(jìn)一步的處理。官方提供的示例項(xiàng)目sample-controller。
這個(gè)例子主要講述了以下幾個(gè)方面：

如何使用自定義資源定義注冊(cè)Foo類型的新自定義資源（自定義資源類型）

如何創(chuàng)建/獲取/列出新資源類型Foo實(shí)例

如何在資源處理創(chuàng)建/更新/刪除事件上設(shè)置控制器

編寫crd controller之前，一定要使用k8s官方提供的代碼生成工具k8s.io/code-generator 去生成 client, informers, listers and deep-copy函數(shù).不僅代碼風(fēng)格符合k8s，而且減少出錯(cuò)和減少工作量都是有很大的幫助。

在項(xiàng)目中使用代碼生成器

下面展示了代碼生成工具是如何工作的以及如何使用最少的代碼行將它們應(yīng)用到自己的項(xiàng)目中，從而為您生成 deepcopy 函數(shù)/typed clients/listers/informer，所有這些的生成僅需要一個(gè) shell 腳本調(diào)用和部分代碼注釋。
不要覺得代碼生成有多么復(fù)雜，其實(shí)官方已經(jīng)做了很多工作了，提供了 generator-group.sh。看過client-go的gopher應(yīng)該都知道項(xiàng)目中有大量代碼工具生成的代碼。
執(zhí)行./hack/update-codegen.sh,即

#!/usr/bin/env bash

# Copyright 2017 The Kubernetes Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

set -o errexit
set -o nounset
set -o pipefail

SCRIPT_ROOT=$(dirname ${BASH_SOURCE})/..
CODEGEN_PKG=${CODEGEN_PKG:-$(cd ${SCRIPT_ROOT}; ls -d -1 ./vendor/k8s.io/code-generator 2>/dev/null || echo ../code-generator)}

# generate the code with:
# --output-base    because this script should also be able to run inside the vendor dir of
#                  k8s.io/kubernetes. The output-base is needed for the generators to output into the vendor dir
#                  instead of the $GOPATH directly. For normal projects this can be dropped.
${CODEGEN_PKG}/generate-groups.sh "deepcopy,client,informer,lister" 
  k8s.io/canary-controller/pkg/client k8s.io/canary-controller/pkg/apis 
  canarycontroller:v1alpha1 
  --output-base "$(dirname ${BASH_SOURCE})/../../.." 
  --go-header-file ${SCRIPT_ROOT}/hack/boilerplate.go.txt

# To use your own boilerplate text use:
#   --go-header-file ${SCRIPT_ROOT}/hack/custom-boilerplate.go.txt

update-codegen腳本將自動(dòng)生成下面的文件和路徑

pkg/apis/canarycontroller/v1alpha1/zz_generated.deepcopy.go

pkg/client/

腳本運(yùn)行后大體會(huì)建立如下的包管理結(jié)構(gòu)：

是不是很簡(jiǎn)單？pkg/client 代碼是被完全生成的，就像包含我們的 CustomResource golang語言類型的 types.go 文件下面的 zz_generated.deepcopy.go 文件一樣,然后你就可以基于生成的代碼寫自己的controller了。
不過并不是不需要自己寫一點(diǎn)代碼，畢竟機(jī)器沒有智能到你定義了什么樣子的crd。所有以下幾個(gè)文件需要自己來定義和實(shí)現(xiàn)，均是和你自己的業(yè)務(wù)邏輯相關(guān)。
pkg/apis以下的除zz_generated.deepcopy.go以外的所有文件。
比如：
types.go

 /*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package v1alpha1

import (
    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// Canary is a specification for a Foo resource
type Canary struct {
    metav1.TypeMeta   `json:",inline"`
    metav1.ObjectMeta `json:"metadata,omitempty"`

    Spec   CanarySpec   `json:"spec"`
    Status CanaryStatus `json:"status"`
}

// CanarySpec is the spec for a Foo resource
type CanarySpec struct {
    DeploymentName string `json:"deploymentName"`
    Replicas       *int32 `json:"replicas"`
}

// CanaryStatus is the status for a Foo resource
type CanaryStatus struct {
    AvailableReplicas int32 `json:"availableReplicas"`
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// CanaryList is a list of Foo resources
type CanaryList struct {
    metav1.TypeMeta `json:",inline"`
    metav1.ListMeta `json:"metadata"`

    Items []Canary `json:"items"`
}

registry.go

/*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package v1alpha1

import (
    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    "k8s.io/apimachinery/pkg/runtime"
    "k8s.io/apimachinery/pkg/runtime/schema"

    canarycontroller "k8s.io/canary-controller/pkg/apis/canarycontroller"
)

// SchemeGroupVersion is group version used to register these objects
var SchemeGroupVersion = schema.GroupVersion{Group: canarycontroller.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 = runtime.NewSchemeBuilder(addKnownTypes)
    AddToScheme   = SchemeBuilder.AddToScheme
)

// Adds the list of known types to Scheme.
func addKnownTypes(scheme *runtime.Scheme) error {
    scheme.AddKnownTypes(SchemeGroupVersion,
        &Canary{},
        &CanaryList{},
    )
    metav1.AddToGroupVersion(scheme, SchemeGroupVersion)
    return nil
}

更多相關(guān)細(xì)節(jié)

見 Kubernetes Deep Dive: Code Generation for CustomResources給出了具體的步驟和關(guān)于tag的標(biāo)注。

總結(jié)

基于crd以及crd controller可以抽象很多業(yè)務(wù)場(chǎng)景。接下我司準(zhǔn)備實(shí)現(xiàn)一個(gè)部署策略相關(guān)的項(xiàng)目。