背景 ECI容器组实例创建过程中，大部分时间消耗在镜像下载阶段，为加速ECI容器组创建速度，ECI提供镜像缓存功能，用户事先将需要用到的镜像作为云盘快照缓存，在创建ECI容器组实例时基于快照创建，避免或减少镜像层下载，从而提升ECI容器组实例创建速度。经实测，基于dockerhub的flink镜像（386.26MB）创建Pod，普通创建eci过程中，镜像准备阶段需要耗费50s，使用镜像快照后镜像准备阶段仅需5s。因此在创建eci过程中，镜像准备阶段节省时间45s。具体的提升速度跟Pod使用的镜像个数，镜像大小和镜像仓库网络因素决定。

为方便kubernetes用户也可以使用到ECI的镜像缓存功能，因此以CRD的方式将ECI镜像缓存功能暴露给kubernetes用户。重点强调：ImageCache CRD在kubernetes集群中为Cluster级别的资源，类似于PV，被集群内所有namespace共享。

准备工作 验证您的kubernetes集群是否支持ImageCache:

$ kubectl get crd/imagecaches.eci.alibabacloud.com NAME CREATED AT imagecaches.eci.alibabacloud.com 2019-09-27T01:15:07Z 输出以上信息，证明您的kubernetes集群已经支持ImageCache。

kubectl get crd/imagecaches.eci.alibabacloud.com Error from server (NotFound): customresourcedefinitions.apiextensions.k8s.io "imagecaches.eci.alibabacloud.com" not found 输出以上信息，证明您的kubernetes集群不支持ImageCache，需要升级virtual-kubelet实现支持ImageCache。

virtual-kubelet升级方式：

阿里云 serverless kubernetes集群：由管理员统一负责升级 阿里云 托管 kubernetes集群：用户更新 阿里云 专有 kubernetes集群：用户更新 阿里云 自建 kubernetes集群：用户更新 准备工作完成后，您可以在您的kubernetes集群中，创建ImageCache资源，并且可以使用ImageCache创建Pod。

注：如果您的集群的ImageCache CRD不是最新的，不支持ImageCache CRD新增的参数，建议升级完virtual-kubelet后，执行如下命令：

kubectl apply -f imagecache-crd-sample.yaml imagecache-crd-sample.yaml:

apiVersion: apiextensions.k8s.io/v1beta1 kind: CustomResourceDefinition metadata: name: imagecaches.eci.alibabacloud.com spec: group: eci.alibabacloud.com version: v1 names: kind: ImageCache plural: imagecaches shortNames: - ic categories: - all scope: Cluster subresources: status: {} validation: openAPIV3Schema: required: - spec properties: spec: type: object required: - images properties: imagePullSecrets: type: array items: type: string images: minItems: 1 type: array items: type: string imageCacheSize: type: integer retentionDays: type: integer additionalPrinterColumns: - name: Age type: date JSONPath: .metadata.creationTimestamp - name: CacheId type: string JSONPath: .status.imageCacheId - name: Phase type: string JSONPath: .status.phase - name: Progress type: string JSONPath: .status.progress ImageCache基本操作 创建 CustomResourceDefinition 对象后，您可以操作ImageCache资源。

ImageCache全参数YAML文件：

apiVersion: eci.alibabacloud.com/v1 kind: ImageCache metadata: name: imagecache-sample spec: images: - centos:latest - busybox:latest imagePullSecrets: - default:secret1 - default:secret2 - kube-system:secret3 imageCacheSize: 25 retentionDays: 7 参数说明：

名称 类型 必选 描述 spec.images []string Y 镜像列表 spec.imagePullSecrets []string N 镜像仓库对应的Secret列表, 格式：。如果images列表中有用户私有仓库镜像，需要用户为私有镜像仓库创建secret，然后根据namespace:secretName格式，设置此参数。如若images中均是共有镜像，不需要设置此参数 spec.imageCacheSize int N 镜像缓存使用的快照盘大小，默认为20GB，取值范围为:[20, 32768]，单位为GB spec.retentionDays int N 镜像缓存保留的时间，取值范围[1,65536]，默认永不过期。 创建ImageCache 创建ImageCahce：

kubectl create -f imagecache-secrets-test.yaml

apiVersion: eci.alibabacloud.com/v1 kind: ImageCache metadata: name: imagecache-sample-liu spec: images: - centos:latest - busybox:latest imagePullSecrets: - default:secret1 - default:secret2 - kube-system:secret3 imageCacheSize: 25 retentionDays: 7 查看ImageCache状态：

liumihustdeMacBook-Pro:vk-debug liumihust$ kubectl get imagecache imagecache-sample-liu NAME AGE CACHEID PHASE PROGRESS imagecache-sample-liu 20h imc-2zeditzeoemfhqor4rf8 Ready 100% 查询ImageCache 获取Cluster下全部ImageCache列表：

kubectl get imagecache imagecache-sample-liu -o yaml 查看ImageCache详情（包括属性、状态以及事件）：

$ kubectl get imagecache/imagecache-secrets-test -o yaml apiVersion: eci.alibabacloud.com/v1 kind: ImageCache metadata: creationTimestamp: "2019-10-24T13:40:56Z" generation: 1 name: imagecache-sample-liu resourceVersion: "212484735" selfLink: /apis/eci.alibabacloud.com/v1/imagecaches/imagecache-sample-liu uid: e83a1c53-f663-11e9-a0d4-fa13fc175b32 spec: imageCacheSize: 25 images: - busybox:latest - nginx status: events: - count: 1 eventTime: null firstTimestamp: "2019-10-24T13:41:40Z" involvedObject: {} lastTimestamp: "2019-10-24T13:41:40Z" message: Success pull image busybox:latest metadata: creationTimestamp: null name: busybox:latest reportingComponent: "" reportingInstance: "" source: component: kubelet host: eci type: Normal - count: 1 eventTime: null firstTimestamp: "2019-10-24T13:42:04Z" involvedObject: {} lastTimestamp: "2019-10-24T13:42:04Z" message: Success pull image nginx metadata: creationTimestamp: null name: nginx reportingComponent: "" reportingInstance: "" source: component: kubelet host: eci type: Normal - count: 1 eventTime: null firstTimestamp: "2019-10-24T13:42:06Z" involvedObject: {} lastTimestamp: "2019-10-24T13:42:06Z" message: Success pull image registry-vpc.cn-beijing.aliyuncs.com/acs/pause-amd64:3.0 metadata: creationTimestamp: null name: registry-vpc.cn-beijing.aliyuncs.com/acs/pause-amd64:3.0 reportingComponent: "" reportingInstance: "" source: component: kubelet host: eci type: Normal imageCacheId: imc-2zeditzeoemfhqor4rf8 expireDateTime: "2019-10-25T13:40:54Z" lastUpdatedTime: "2019-10-24T13:44:17Z" phase: Ready progress: 100% startTime: "2019-10-24T13:40:58Z" ImageCache快速创建Pod ImageCache资源是Cluster级别的，所以在不同的namespace下创建Pod都可以使用ImageCache实现创建Pod。

使用ImageCache快速创建Pod有两种使用方式：

明确指定方式：在创建pod时，明确的指定使用哪个ImageCacheId创建Pod 自动匹配方式：在创建Pod时，根据匹配策略自动选择最优的ImageCache创建Pod 明确指定方式 这种使用方式，有一个前提条件就是ImageCache状态必须为Ready状态，其他状态的ImageCache会导致Pod创建失败。

Deployment使用方式：

在PodTemplate增加Annotation关联ImageCache：

apiVersion: apps/v1 kind: Deployment metadata: name: nginx-deployment labels: app: nginx spec: replicas: 2 selector: matchLabels: app: nginx template: metadata: labels: app: nginx annotations: k8s.aliyun.com/eci-image-snapshot-id: imc-2ze5tm5gehgtiigaz5jh spec: nodeName: virtual-kubelet containers: - name: nginx image: nginx:1.7.9 imagePullPolicy: IfNotPresent Pod使用方式：

在Pod的Yaml文件中增加Annotation关联ImageCache：

apiVersion: v1 kind: Pod metadata: annotations: k8s.aliyun.com/eci-image-snapshot-id: imc-2ze5tm5gehgtiigaz5jh name: nginx-imagecache-id spec: containers: - image: nginx:1.7.9 imagePullPolicy: IfNotPresent name: nginx resources: limits: cpu: 300m memory: 200Mi requests: cpu: 200m memory: 100Mi nodeName: virtual-kubelet 自动匹配方式 在创建Pod时，用户通过Annotation方式，声明使用自动匹配ImageCache方式快速创建Pod，ECI管控基于用户已有的ImageCache列表依据策略进行匹配，匹配出最优的ImageCache创建Pod。如果没有匹配到合适的ImageCache，执行正常下载镜像创建Pod流程。

目前匹配策略的优先级从高到底：

镜像匹配度 匹配的镜像大小 创建时间 Deployment使用方式：

在PodTemplate增加Annotation关联ImageCache，告知ECI管控在创建Pod时是否启用自动匹配ImageCache：

apiVersion: apps/v1 kind: Deployment metadata: name: nginx-deployment labels: app: nginx spec: replicas: 2 selector: matchLabels: app: nginx template: metadata: labels: app: nginx annotations: k8s.aliyun.com/eci-image-cache: "true" spec: nodeName: virtual-kubelet containers: - name: nginx image: nginx:1.7.9 imagePullPolicy: IfNotPresent Pod使用方式：

基于Annotation方式，在Pod的Yaml文件中增加Annotation：

apiVersion: v1 kind: Pod metadata: annotations: k8s.aliyun.com/eci-image-cache: "true" name: nginx-auto-match spec: containers: - image: nginx:1.7.9 imagePullPolicy: IfNotPresent name: nginx resources: limits: cpu: 300m memory: 200Mi requests: cpu: 200m memory: 100Mi nodeName: virtual-kubelet 使用建议 Pod中容器的image建议采用ImageCache中镜像，提高匹配度。 Pod中容器的ImagePullPolicy建议设置为IfNotPresent，避免镜像层重复下载。 Tip: 在创建Pod时，k8s.aliyun.com/eci-image-snapshot-id和k8s.aliyun.com/eci-image-cache同时设置时，明确指定方式优先级高于自动匹配方式

注：如果是deployment，使用cache的Annotation应该放在pod级别，而不是放在deployment级别，否则会设置失效。

删除ImageCache 删除ImageCache时，不影响基于ImageCache创建成功的Pod实例。

操作如下：

$ kubectl get imagecache/imagecache-secrets-test NAME AGE CACHEID PHASE PROGRESS imagecache-secrets-test 14h imc-2ze5tm5gehgtjru0kfm8 Ready 100% $ kubectl delete imagecache/imagecache-secrets-test imagecache.eci.alibabacloud.com " imagecache-secrets-test" deleted $ kubectl get imagecache/ imagecache-secrets-test Error from server (NotFound): imagecaches.eci.alibabacloud.com " imagecache-secrets-test" not found kubernetes ImageCache API文档 Group Version Kind eci.alibabacloud.com v1 ImageCache ImageCache v1 eci.alibabacloud.com ImageCacheList:

Field Type Description apiVersion string api版本: eci.alibabacloud.com/v1 kind string 资源类别: ImageCacheList metadata ListMeta Standard list metadata. Items []ImageCache 镜像缓存列表 ImageCache:

Field Type Description apiVersion string api版本: eci.alibabacloud.com/v1 kind string 资源类别: ImageCache metadata ObjectMeta spec ImageCacheSpec 镜像缓存详细信息 status ImageCacheStatus 镜像缓存状态信息 ImageCacheSpec:

Field Type Request Description images []string Y 镜像缓存的镜像列表 imagePullSecrets []string N 私有镜像仓库对应的Secret列表，格式：namespace:secretName imageCacheSize int N 镜像缓存的大小，默认为20GB，取值范围为:[20, 32768]，单位为GB retentionDays int N 镜像缓存保留的时间，取值范围[1,65536]，默认永不过期。 ImageCacheStatus:

Field Type Description phase string 镜像缓存状态 progress string 标示制作过程中进度 imageCacheId string 镜像缓存ID，调用Provdier的Create操作返回，然后更新到ImageCache对象 startTime Time 镜像缓存对象创建时间 lastUpdatedTime Time 镜像缓存最后更新时间 events []Event 制作镜像cache过程中的事件信息 expireDateTime Time 镜像缓存的过期时间，有两种来源：1、用户设置了retentionDays；2、制作失败的镜像缓存自动在24小时后过期。 CreateImageCache 创建镜像缓存对象

Http Request POST /apis/eci.alibabacloud.com/v1/imagecaches

curl request example curl -X POST -H 'Content-Type: application/yaml' --data ' apiVersion: eci.alibabacloud.com/v1 kind: ImageCache metadata: name: imagecache-secrets-test spec: images: - registry.cn-shanghai.aliyuncs.com/baz/nginx:1.0 imagePullSecrets: - default:acr-test ' http://127.0.0.1:8001/apis/eci.alibabacloud.com/v1/imagecaches curl response example { "apiVersion": "eci.alibabacloud.com/v1", "kind": "ImageCache", "metadata": { "creationTimestamp": "2019-10-10T03:50:47Z", "generation": 1, "name": "imagecache-secrets-test", "resourceVersion": "647052328", "selfLink": "/apis/eci.alibabacloud.com/v1/imagecaches/imagecache-secrets-test11", "uid": "2506ba37-eb11-11e9-9576-f2ef49bf1a08" }, "spec": { "imagePullSecrets": [ "default:acr-test" ], "images": [ "registry.cn-shanghai.aliyuncs.com/baz/nginx:1.0" ] } } ListImageCache 获取镜像缓存列表

Http Request GET /apis/eci.alibabacloud.com/v1/imagecaches

curl request example curl -X GET 'http://127.0.0.1:8001/apis/eci.alibabacloud.com/v1/imagecaches' curl response example { "apiVersion": "eci.alibabacloud.com/v1", "items": [ { "apiVersion": "eci.alibabacloud.com/v1", "kind": "ImageCache", "metadata": { "annotations": { "kubectl.kubernetes.io/last-applied-configuration": "{"apiVersion":"eci.alibabacloud.com/v1","kind":"ImageCache","metadata":{"annotations":{},"name":"imagecache-secrets-test"},"spec":{"imagePullSecrets":["default:acr-test"],"images":["registry.cn-shanghai.aliyuncs.com/baz/nginx:1.0"]}}\n" }, "creationTimestamp": "2019-10-10T01:43:48Z", "generation": 1, "name": "imagecache-secrets-test", "resourceVersion": "646375979", "selfLink": "/apis/eci.alibabacloud.com/v1/imagecaches/imagecache-secrets-test", "uid": "67460461-eaff-11e9-9774-b2c06862f69a" }, "spec": { "imagePullSecrets": [ "default:acr-test" ], "images": [ "registry.cn-shanghai.aliyuncs.com/baz/nginx:1.0" ] }, "status": { "imageCacheId": "imc-2ze5xnx4yiply807zo0o", "lastUpdatedTime": "2019-10-10T01:47:14Z", "phase": "Ready", "progress": "100%", "startTime": "2019-10-10T01:43:49Z" } } ], "kind": "ImageCacheList", "metadata": { "continue": "", "resourceVersion": "647062964", "selfLink": "/apis/eci.alibabacloud.com/v1/imagecaches" } } GetImageCache 获取某一个镜像缓存的相信信息

Http Request GET /apis/eci.alibabacloud.com/v1/imagecaches/{name}

curl request example curl -X GET 'http://127.0.0.1:8001/apis/eci.alibabacloud.com/v1/imagecaches/imagecache-secrets-test' curl response example { "apiVersion": "eci.alibabacloud.com/v1", "kind": "ImageCache", "metadata": { "annotations": { "kubectl.kubernetes.io/last-applied-configuration": "{"apiVersion":"eci.alibabacloud.com/v1","kind":"ImageCache","metadata":{"annotations":{},"name":"imagecache-secrets-test"},"spec":{"imagePullSecrets":["default:acr-test"],"images":["registry.cn-shanghai.aliyuncs.com/baz/nginx:1.0"]}}\n" }, "creationTimestamp": "2019-10-10T01:43:48Z", "generation": 1, "name": "imagecache-secrets-test", "resourceVersion": "646375979", "selfLink": "/apis/eci.alibabacloud.com/v1/imagecaches/imagecache-secrets-test", "uid": "67460461-eaff-11e9-9774-b2c06862f69a" }, "spec": { "imagePullSecrets": [ "default:acr-test" ], "images": [ "registry.cn-shanghai.aliyuncs.com/baz/nginx:1.0" ] }, "status": { "imageCacheId": "imc-2ze5xnx4yiply807zo0o", "lastUpdatedTime": "2019-10-10T01:47:14Z", "phase": "Ready", "progress": "100%", "startTime": "2019-10-10T01:43:49Z" } } DeleteImageCache 删除指定镜像缓存

Http Request DELETE /apis/eci.alibabacloud.com/v1/imagecaches/{name}

curl request example curl -X DELETE -H 'Content-Type: application/yaml' 'http://127.0.0.1:8001/apis/eci.alibabacloud.com/v1/imagecaches/imagecache-secrets-test' curl response example "kind": "Status", "apiVersion": "v1", "metadata": {}, "status": "Success", "details": { "name": "imagecache-secrets-test", "group": "eci.alibabacloud.com", "kind": "imagecaches", "uid": "67460461-eaff-11e9-9774-b2c06862f69a" } }