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kubernetes自定义资源对象再极大程度提高了API Server的可扩展性,让企业能够根据业务需求通过CRD编写controller或者operator来实现生产中各种特殊场景。随着k8s的版本升级,CRD的功能也越来越完善,下面对其中几点进行说明。
以下验证kubernetes版本为1.13.2,docker版本:18.09.5
Validation(验证)
在项目中用自定义资源对象时,如果创建自定义资源时某些字段不符合要求,会导致监听该资源对象的controller或者operator出现异常,解析结构体报错,所以Validation这个功能非常实用,在创建时就进行校验,减少后面的排错和异常处理的麻烦。
可以通过 OpenAPI v3 schema(https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#schemaObject)验证自定义对象是否符合标准 。此外,以下限制适用于 schema:
可以使用 kube-apiserver CustomResourceValidation 上的功能门(feature gate)禁用此功能:
--feature-gates=CustomResourceValidation=false
从以下特性门参数说明地址,可以看到Validation功能在k8s 1.8版本就已经有了,但是CustomResourceValidation特性门是默认false,1.9Beta之后版本默认为true
https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/
以下示例将大概对该功能进行应用和说明,在以下示例中,CustomResourceDefinition 对自定义对象应用以下验证:
将以下内容保存到 redis-cluster-crd.yaml:
apiVersion: apiextensions.k8s.io/v1beta1kind: CustomResourceDefinitionmetadata: name: redisclusters.redis.middleware.hc.cnspec: group: redis.middleware.hc.cn versions: - name: v1alpha1 # Each version can be enabled/disabled by Served flag. served: true # One and only one version must be marked as the storage version. storage: true scope: Namespaced names: kind: RedisCluster singular: rediscluster listKind: RedisClusterList plural: redisclusters shortNames: - rec # 执行kubectl get all时会查到pod、service、该crd等属于all categories的资源对象 categories: - all validation: # openAPIV3Schema 适用于验证自定义对象的 schema。 openAPIV3Schema: properties: spec: required: ["replicas", "repository", "version"] properties: pause: type: boolean replicas: type: integer minimum: 0 maximum: 50 # 偶数 multipleOf: 2 updateStrategy: type: object properties: type: type: string # 枚举 enum: ["AssignReceive", "AutoReceive"] pipeline: type: string pattern: '^([1-9][0-9]*){1,3}$' assignStrategies: type: array items: type: object properties: slots: type: integer minimum: 1 maximum: 16384 fromReplicas: type: string # 至少匹配3位,a-z或者0-9或者, pattern: '^[a-z0-9,]{3,}$' pod: type: array items: type: object required: ["configmap", "middlewareImage", "initImage"] properties: configmap: type: string monitorImage: type: string initImage: type: string middlewareImage: type: string
创建它:
kubectl create -f redis-cluster-crd.yaml
默认不加validation时,在创建自定义资源对象时,不会校验,有些字段没有了(如spec.replicas)都可以正常被创建,为了减少排错的难度和operator、controller的麻烦的检验,所以在创建自定义资源定义时,就把validation加上。以上的检验应该覆盖到了常见的检验场景,其他场景可以自己摸索。具体还可以参考kubernetes源码,1.13.2版本kubernetes源码位于types.go第327行CustomResourceValidation结构体:
$GOPATH/src/k8s.io/kubernetes/staging/src/k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/types.go
将以下YAML保存到redis-cluster-cr.yaml:
apiVersion: redis.middleware.hc.cn/v1alpha1kind: RedisClustermetadata: name: example000-redis-cluster namespace: kube-systemspec: # 代表redis集群的个数 replicas: 3 # 代表是否进入维修状态 pause: true repository: library/redis # 镜像版本,便于后续多版本特化支持 version: 3.2.6 #redis集群升级策略 updateStrategy: # 升级类型为AutoReceive(自动分配,不用AssignStrategies), AssignReceive(指定值分配,需要用AssignStrategies) type: AssignReceive1 pipeline: "100a" assignStrategies: - slots: 0 fromReplicas: nodeId1 - # 从nodeId3,nodeId4一共分配1000个卡槽 slots: 1000 # 多个nodeId用逗号分隔 fromReplicas: nodeId3,nodeId4 # redis 实例配置详情 pod: # 配置文件模板名 - configmap: example000-redis-cluster-config # 监控镜像 monitorImage: redis-exporter:v1 # 初始化镜像 #initImage: redis-init:v1 # 中间件容器镜像 middlewareImage: redis-trib:3.2.6
并创建它:
kubectl create -f redis-cluster-cr.yaml
会发现报以下错误:
如果所有字段都符合校验逻辑,才可以创建对象。将以下 YAML 保存到 redis-cluster-cr.yaml:
apiVersion: redis.middleware.hc.cn/v1alpha1kind: RedisClustermetadata: name: example000-redis-cluster namespace: kube-systemspec: # 代表redis集群的个数 replicas: 6 # 代表是否进入维修状态 pause: true repository: library/redis # 镜像版本,便于后续多版本特化支持 version: 3.2.6 #redis集群升级策略 updateStrategy: # 升级类型为AutoReceive(自动分配,不用AssignStrategies), AssignReceive(指定值分配,需要用AssignStrategies) type: AssignReceive pipeline: "100" assignStrategies: - slots: 1 fromReplicas: all - # 从nodeId3,nodeId4一共分配1000个卡槽 slots: 1000 # 多个nodeId用逗号分隔 fromReplicas: node1,node2 # redis 实例配置详情 pod: # 配置文件模板名 - configmap: example000-redis-cluster-config # 监控镜像 monitorImage: redis-exporter:v1 # 初始化镜像 initImage: redis-init:v1 # 中间件容器镜像 middlewareImage: redis-trib:3.2.6
并创建它,发现才可以创建:
kubectl apply -f redis-cluster-cr.yamlrediscluster.redis.middleware.hc.cn/example000-redis-cluster configured
Category(分类)
类别是自定义资源所属的分组资源的列表(例如 all)。您可以使用 kubectl get 列出属于该类别的资源。此功能可用于 v1.10 及以上k8s版本自定义资源。
以下示例添加 all CustomResourceDefinition 中的类别列表,并说明如何使用 kubectl get all 输出自定义资源 。
将以下 内容保存到 redis-cluster-crd.yaml中执行:
kubectl apply -f redis-cluster-crd.yaml
apiVersion: apiextensions.k8s.io/v1beta1kind: CustomResourceDefinitionmetadata: name: redisclusters.redis.middleware.hc.cnspec: group: redis.middleware.hc.cn versions: - name: v1alpha1 # Each version can be enabled/disabled by Served flag. served: true # One and only one version must be marked as the storage version. storage: true scope: Namespaced names: kind: RedisCluster singular: rediscluster listKind: RedisClusterList plural: redisclusters shortNames: - rec # 执行kubectl get all时会查到pod、service、该crd等属于all categories的资源对象 categories: - all
将以下内容保存到redis-cluster-cr.yaml中执行
kubectl apply -f redis-cluster-cr.yaml
apiVersion: redis.middleware.hc.cn/v1alpha1kind: RedisClustermetadata: name: example000-redis-cluster namespace: kube-systemspec: # 代表redis集群的个数 replicas: 6 # 代表是否进入维修状态 pause: true repository: library/redis # 镜像版本,便于后续多版本特化支持 version: 3.2.6 #redis集群升级策略 updateStrategy: # 升级类型为AutoReceive(自动分配,不用AssignStrategies), AssignReceive(指定值分配,需要用AssignStrategies) type: AssignReceive pipeline: "100" assignStrategies: - slots: 2000 fromReplicas: nodeId1 - # 从nodeId3,nodeId4一共分配1000个卡槽 slots: 1000 # 多个nodeId用逗号分隔 fromReplicas: nodeId3,nodeId4 # redis 实例配置详情 pod: # 配置文件模板名 - configmap: example000-redis-cluster-config # 监控镜像 monitorImage: redis-exporter:v1 # 初始化镜像 initImage: redis-init:v1 # 中间件容器镜像 middlewareImage: redis-trib:3.2.6
执行以下命令查看:
kubectl get all -nkube-system
时会查到pod、service、该crd等属于all categories的资源对象。(这个可能得等几分钟才能生效)
子资源
status子资源
启用状态子资源后,将公开自定义资源的子资源 /status。
在code-generator生成代码时会生成,如下方法:
// RedisClusterInterface has methods to work with RedisCluster resources.type RedisClusterInterface interface { Create(*v1alpha1.RedisCluster) (*v1alpha1.RedisCluster, error) Update(*v1alpha1.RedisCluster) (*v1alpha1.RedisCluster, error) UpdateStatus(*v1alpha1.RedisCluster) (*v1alpha1.RedisCluster, error) ......}
scale子资源
启用 scale 子资源后,将公开自定义资源的子资源 /scale。该 autoscaling/v1.Scale 对象作为有效负载发送 /scale。
要启用 scale 子资源,CustomResourceDefinition 中需要定义以下值。
在以下示例中,启用了status 和 scale 子资源。将以下内容保存到redis-cluster-crd.yaml并创建 kubectl apply -f redis-cluster-crd.yaml:
apiVersion: apiextensions.k8s.io/v1beta1kind: CustomResourceDefinitionmetadata: name: redisclusters.redis.middleware.hc.cnspec: group: redis.middleware.hc.cn versions: - name: v1alpha1 # Each version can be enabled/disabled by Served flag. served: true # One and only one version must be marked as the storage version. storage: true scope: Namespaced names: kind: RedisCluster singular: rediscluster listKind: RedisClusterList plural: redisclusters shortNames: - rec # 执行kubectl get all时会查到pod、service、该crd等属于all categories的资源对象 categories: - all subresources: # status enables the status subresource. status: {} scale: # specReplicasPath defines the JSONPath inside of a custom resource that corresponds to Scale.Spec.Replicas. specReplicasPath: .spec.replicas # statusReplicasPath defines the JSONPath inside of a custom resource that corresponds to Scale.Status.Replicas. statusReplicasPath: .status.replicas # labelSelectorPath defines the JSONPath inside of a custom resource that corresponds to Scale.Status.Selector. labelSelectorPath: .status.labelSelector
创建 CustomResourceDefinition 对象后,您可以创建自定义对象。
如果您将以下 YAML 保存到 redis-cluster-cr.yaml:
apiVersion: redis.middleware.hc.cn/v1alpha1kind: RedisClustermetadata: name: example000-redis-cluster namespace: kube-systemspec: # 代表redis集群的个数 replicas: 6 # 代表是否进入维修状态 pause: true repository: library/redis # 镜像版本,便于后续多版本特化支持 version: 3.2.6 #redis集群升级策略 updateStrategy: # 升级类型为AutoReceive(自动分配,不用AssignStrategies), AssignReceive(指定值分配,需要用AssignStrategies) type: AssignReceive pipeline: "100" assignStrategies: - slots: 2000 fromReplicas: nodeId1 - # 从nodeId3,nodeId4一共分配1000个卡槽 slots: 1000 # 多个nodeId用逗号分隔 fromReplicas: nodeId3,nodeId4 # redis 实例配置详情 pod: # 配置文件模板名 - configmap: example000-redis-cluster-config # 监控镜像 monitorImage: redis-exporter:v1 # 初始化镜像 initImage: redis-init:v1 # 中间件容器镜像 middlewareImage: redis-trib:3.2.6
并创建它:
kubectl create -f redis-cluster-cr.yaml
然后在以下位置创建新的命名空间 RESTful API 端点:
/apis/redis.middleware.hc.cn/v1alpha1/namespaces/kube-system/redisclusters/example000-redis-cluster/status
和
/apis/redis.middleware.hc.cn/v1alpha1/namespaces/kube-system/redisclusters/example000-redis-cluster/scale
可以使用该 kubectl scale 命令缩放自定义资源。例如,以上创建的自定义资源的的 .spec.replicas 设置为 10:
# kubectl get rec --all-namespacesNAMESPACE NAME DESIRED PAUSE AGEkube-system example000-redis-cluster 6 true 10h
# kubectl scale --replicas=10 rec/example000-redis-cluster -nkube-systemrediscluster.redis.middleware.hc.cn/example000-redis-cluster scaled
# kubectl get rec --all-namespacesNAMESPACE NAME DESIRED PAUSE AGEkube-system example000-redis-cluster 10 true 10h
# kubectl get rec example000-redis-cluster -n kube-system -o jsonpath='{.spec.replicas}'10
打印其他列
从 Kubernetes 1.11 开始,kubectl 使用服务器端打印。服务器决定 kubectl get 命令显示哪些列。您可以使用 CustomResourceDefinition 自定义这些列。下面的示例将输出 Spec、Replicas 和 Age 列。
将 CustomResourceDefinition保存到 redis-cluster-crd.yaml。
apiVersion: apiextensions.k8s.io/v1beta1kind: CustomResourceDefinitionmetadata: name: redisclusters.redis.middleware.hc.cnspec: group: redis.middleware.hc.cn versions: - name: v1alpha1 # Each version can be enabled/disabled by Served flag. served: true # One and only one version must be marked as the storage version. storage: true scope: Namespaced names: kind: RedisCluster singular: rediscluster listKind: RedisClusterList plural: redisclusters shortNames: - rec # 执行kubectl get all时会查到pod、service、该crd等属于all categories的资源对象 categories: - all additionalPrinterColumns: - name: DESIRED type: integer description: The number of statefulset managed by the this redisCluster JSONPath: .spec.replicas # boolean,date,integer,number,string - name: PAUSE type: boolean description: Whether this redisCluster's grandson (pod) will not be managed by statefulset JSONPath: .spec.pause
创建 CustomResourceDefinition:
kubectl create -f redis-cluster-crd.yaml
使用上面创建的 redis-cluster-cr.yaml 实例。查看打印:
kubectl get rec --all-namespaces
请注意 NAME、NAMESPACE, DESIRED、PAUSE 和 AGE 在输出列,并且都被转成了大写字母:
[root@master-192 redis-container]# kubectl get rec --all-namespacesNAMESPACE NAME DESIRED PAUSE AGEkube-system example000-redis-cluster 6 true 10h
NAME和NAMESPACE 列是隐含的,不需要在CustomResourceDefinition 中定义。
operator中应用该特性
在golang编写的operator代码中创建该结构体:
//创建CRDfunc CreateRedisClusterCRD(extensionCRClient *extensionsclient.Clientset) error { //add CustomResourceValidation due to guarantee redis operator work normally labelSelectorPath := ".status.labelSelector" replicasMinimum := float64(0) replicasMaximum := float64(50) replicasMultipleOf := float64(2) slotsMinimum := float64(1) slotsMaximum := float64(16384) assignStr := "AssignReceive" autoStr := "AutoReceive" assignJson, _ := json.Marshal(assignStr) autoJson, _ := json.Marshal(autoStr)
/*
* 提示:该行代码过长,系统自动注释不进行高亮。一键复制会移除系统注释
* crd := &v1beta1.CustomResourceDefinition{ ObjectMeta: metav1.ObjectMeta{ Name: "redisclusters." + v1alpha1.SchemeGroupVersion.Group, }, Spec: v1beta1.CustomResourceDefinitionSpec{ Group: v1alpha1.SchemeGroupVersion.Group, Versions: []v1beta1.CustomResourceDefinitionVersion { { // Served is a flag enabling/disabling this version from being served via REST APIs Served: true, Name: v1alpha1.SchemeGroupVersion.Version, // Storage flags the version as storage version. There must be exactly one flagged as storage version Storage: true, }, }, Scope: v1beta1.NamespaceScoped, Names: v1beta1.CustomResourceDefinitionNames{ Kind: "RedisCluster", ListKind: "RedisClusterList", Plural: "redisclusters", Singular: "rediscluster", ShortNames: []string{"rec"}, Categories: []string{"all"}, }, Subresources: &v1beta1.CustomResourceSubresources { Status: &v1beta1.CustomResourceSubresourceStatus {}, Scale: &v1beta1.CustomResourceSubresourceScale { SpecReplicasPath: ".spec.replicas", StatusReplicasPath: ".status.replicas", LabelSelectorPath: &labelSelectorPath, }, }, AdditionalPrinterColumns: []v1beta1.CustomResourceColumnDefinition{ { Name: "DESIRED", Type: "integer", Description: "The number of statefulset managed by the this redisCluster", JSONPath: ".spec.replicas", }, { Name: "PAUSE", Type: "boolean", Description: "Whether this redisCluster's grandson (pod) will not be managed by statefulset", JSONPath: ".spec.pause", }, { Name: "AGE", Type: "date", JSONPath: ".metadata.creationTimestamp", }, }, Validation: &v1beta1.CustomResourceValidation { OpenAPIV3Schema: &v1beta1.JSONSchemaProps { Properties: map[string]v1beta1.JSONSchemaProps { "spec": { Required: []string{"replicas", "repository", "version"}, Properties: map[string]v1beta1.JSONSchemaProps{ "pause": { Type: "boolean", }, "replicas": { Type: "integer", Minimum: &replicasMinimum, Maximum: &replicasMaximum, MultipleOf: &replicasMultipleOf, }, "updateStrategy": { Type: "object", Properties: map[string]v1beta1.JSONSchemaProps{ "type": { Type: "string", Enum: []v1beta1.JSON { { //这里必须是JSON格式的字符串 Raw: assignJson, }, { Raw: autoJson, }, }, }, "pipeline": { Type: "string", Pattern: `^([1-9][0-9]*){1,3}$`, }, "assignStrategies": { Type: "array", Items: &v1beta1.JSONSchemaPropsOrArray{ Schema: &v1beta1.JSONSchemaProps{ Type: "object", Properties: map[string]v1beta1.JSONSchemaProps{ "slots": { Type: "integer", Minimum: &slotsMinimum, Maximum: &slotsMaximum, }, "fromReplicas": { Type: "string", Pattern: `^[a-z0-9,]{3,}$`, }, }, }, }, }, }, }, }, }, "pod": { Type: "array", Items: &v1beta1.JSONSchemaPropsOrArray { Schema: &v1beta1.JSONSchemaProps { Type: "object", Required: []string{"replicas", "repository", "version"}, Properties: map[string]v1beta1.JSONSchemaProps{ "configmap": { Type: "string", }, "monitorImage": { Type: "string", }, "initImage": { Type: "string", }, "middlewareImage": { Type: "string", }, }, }, }, }, }, }, }, }, } _, err := extensionCRClient.ApiextensionsV1beta1().CustomResourceDefinitions().Create(crd) return err}
*/
参考
官方Extend the Kubernetes API with CustomResourceDefinitions:
https://kubernetes.io/docs/tasks/access-kubernetes-api/custom-resources/custom-resource-definitions/
feature-gates参数说明:
https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/
CustomResourceDefinition中文文档:
https://kubernetes.feisky.xyz/cha-jian-kuo-zhan/api/customresourcedefinition
swagger和openAPI: 数据类型:
https://www.breakyizhan.com/swagger/2969.html
正则表达式:
https://www.cnblogs.com/afarmer/archive/2011/08/29/2158860.html
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