Headless Service 简介 有时不需要或不想要Service来负载均衡到多个Pod时，可以通过指定 Cluster IP（spec.clusterIP）的值为 "None" 来创建 Headless Service。
这个选项允许开发人员自由寻找他们自己的方式，从而降低与 Kubernetes 系统的耦合性。 应用仍然可以使用一种自注册的模式和适配器，对其它需要发现机制的系统能够很容易地基于这个 API 来构建。
对这类 Service 并不会分配 Cluster IP，kube-proxy 不会处理它们，而且平台也不会为它们进行负载均衡和路由。 DNS 如何实现自动配置，依赖于 Service 是否定义了 selector。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 （1）编写headless service配置清单 [root@k8s-master mainfests]# cp myapp-svc.yaml myapp-svc-headless.yaml [root@k8s-master mainfests]# vim myapp-svc-headless.yaml apiVersion: v1 kind: Service metadata: name: myapp-headless namespace: default spec: selector: app: myapp release: canary clusterIP: "None" #headless的clusterIP值为None ports: - port: 80 targetPort: 80 （2）创建headless service [root@k8s-master mainfests]# kubectl apply -f myapp-svc-headless.yaml service/myapp-headless created [root@k8s-master mainfests]# kubectl get svc NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 36d myapp NodePort 10.101.245.119 <none> 80:30080/TCP 1h myapp-headless ClusterIP None <none> 80/TCP 5s redis ClusterIP 10.107.238.182 <none> 6379/TCP 2h （3）查看kube-dns的IP [root@k8s-master mainfests]# kubectl get svc -n kube-system NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP 36d （4）使用kube-dns进行解析验证，可见是直接将service的域名解析到关联Pod的IP [root@k8s-master mainfests]# dig -t A myapp-headless.default.svc.cluster.local. @10.96.0.10 ; <<>> DiG 9.9.4-RedHat-9.9.4-61.el7 <<>> -t A myapp-headless.default.svc.cluster.local. @10.96.0.10 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62028 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;myapp-headless.default.svc.cluster.local. IN A ;; ANSWER SECTION: myapp-headless.default.svc.cluster.local. 5 IN A 10.244.1.18 myapp-headless.default.svc.cluster.local. 5 IN A 10.244.1.19 myapp-headless.default.svc.cluster.local. 5 IN A 10.244.2.15 myapp-headless.default.svc.cluster.local. 5 IN A 10.244.2.16 myapp-headless.default.svc.cluster.local. 5 IN A 10.244.2.17 ;; Query time: 4 msec ;; SERVER: 10.96.0.10#53(10.96.0.10) ;; WHEN: Thu Sep 27 04:27:15 EDT 2018 ;; MSG SIZE rcvd: 349 （5）查看Headless Service关联的Pod的IP比对验证 [root@k8s-master mainfests]# kubectl get pods -o wide -l app=myapp NAME READY STATUS RESTARTS AGE IP NODE myapp-deploy-69b47bc96d-4hxxw 1/1 Running 0 1h 10.244.1.18 k8s-node01 myapp-deploy-69b47bc96d-95bc4 1/1 Running 0 1h 10.244.2.16 k8s-node02 myapp-deploy-69b47bc96d-hwbzt 1/1 Running 0 1h 10.244.1.19 k8s-node01 myapp-deploy-69b47bc96d-pjv74 1/1 Running 0 1h 10.244.2.15 k8s-node02 myapp-deploy-69b47bc96d-rf7bs 1/1 Running 0 1h 10.244.2.17 k8s-node02 （6）对比含有ClusterIP的service解析，可见是解析到了Service的ClusterIP [root@k8s-master mainfests]# dig -t A myapp.default.svc.cluster.local. @10.96.0.10 ; <<>> DiG 9.9.4-RedHat-9.9.4-61.el7 <<>> -t A myapp.default.svc.cluster.local. @10.96.0.10 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50445 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;myapp.default.svc.cluster.local. IN A ;; ANSWER SECTION: myapp.default.svc.cluster.local. 5 IN A 10.101.245.119 ;; Query time: 1 msec ;; SERVER: 10.96.0.10#53(10.96.0.10) ;; WHEN: Thu Sep 27 04:31:16 EDT 2018 ;; MSG SIZE rcvd: 107 （7）查看Service的ClusterIP比对验证 [root@k8s-master mainfests]# kubectl get svc NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 36d myapp NodePort 10.101.245.119 <none> 80:30080/TCP 1h myapp-headless ClusterIP None <none> 80/TCP 11m redis ClusterIP 10.107.238.182 <none> 6379/TCP 2h
从以上的演示可以看到对比普通的service和headless service，headless service做dns解析是直接解析到pod的，而servcie是解析到ClusterIP的，那么headless有什么用呢？？？
这将在statefulset中应用到。
statefulset简介 从前面的学习我们知道使用Deployment创建的pod是无状态的，当挂载了Volume之后，如果该pod挂了，Replication Controller会再启动一个pod来保证可用性，但是由于pod是无状态的，pod挂了就会和之前的Volume的关系断开，新创建的Pod无法找到之前的Pod。但是对于用户而言，他们对底层的Pod挂了是没有感知的，但是当Pod挂了之后就无法再使用之前挂载的存储卷。
为了解决这一问题，就引入了StatefulSet用于保留Pod的状态信息。
StatefulSet是为了解决有状态服务的问题（对应Deployments和ReplicaSets是为无状态服务而设计），其应用场景包括：
稳定的持久化存储，即Pod重新调度后还是能访问到相同的持久化数据，基于PVC来实现
稳定的网络标志，即Pod重新调度后其PodName和HostName不变，基于Headless Service（即没有Cluster IP的Service）来实现
有序部署，有序扩展，即Pod是有顺序的，在部署或者扩展的时候要依据定义的顺序依次依次进行（即从0到N-1，在下一个Pod运行之前所有之前的Pod必须都是Running和Ready状态），基于init containers来实现
有序收缩，有序删除（即从N-1到0）
有序的滚动更新
从上面的应用场景可以发现，StatefulSet由以下几个部分组成：
Headless Service（无头服务）用于为Pod资源标识符生成可解析的DNS记录。
volumeClaimTemplates （存储卷申请模板）基于静态或动态PV供给方式为Pod资源提供专有的固定存储。
StatefulSet，用于管控Pod资源。
为什么要有headless？ 在deployment中，每一个pod是没有名称，是随机字符串，是无序的。而statefulset中是要求有序的，每一个pod的名称必须是固定的。当节点挂了，重建之后的标识符是不变的，每一个节点的节点名称是不能改变的。pod名称是作为pod识别的唯一标识符，必须保证其标识符的稳定并且唯一。
为了实现标识符的稳定，这时候就需要一个headless service 解析直达到pod，还需要给pod配置一个唯一的名称。
为什么要 有volumeClainTemplate？？ 大部分有状态副本集都会用到持久存储，比如分布式系统来说，由于数据是不一样的，每个节点都需要自己专用的存储节点。而在deployment中pod模板中创建的存储卷是一个共享的存储卷，多个pod使用同一个存储卷，而statefulset定义中的每一个pod都不能使用同一个存储卷，由此基于pod模板创建pod是不适应的，这就需要引入volumeClainTemplate，当在使用statefulset创建pod时，会自动生成一个PVC，从而请求绑定一个PV，从而有自己专用的存储卷。Pod名称、PVC和PV关系图如下：
StatefulSet使用示例 在创建StatefulSet之前需要准备的东西，值得注意的是创建顺序非常关键，创建顺序如下：
Volume
Persistent Volume
Persistent Volume Claim
Service
StatefulSet
Volume可以有很多种类型，比如nfs、glusterfs等，我们这里使用的ceph RBD来创建。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 [root@k8s-master ~]# kubectl explain statefulset KIND: StatefulSet VERSION: apps/v1 DESCRIPTION: StatefulSet represents a set of pods with consistent identities. Identities are defined as: - Network: A single stable DNS and hostname. - Storage: As many VolumeClaims as requested. The StatefulSet guarantees that a given network identity will always map to the same storage identity. FIELDS: apiVersion <string> kind <string> metadata <Object> spec <Object> status <Object> [root@k8s-master ~]# kubectl explain statefulset.spec KIND: StatefulSet VERSION: apps/v1 RESOURCE: spec <Object> DESCRIPTION: Spec defines the desired identities of pods in this set. A StatefulSetSpec is the specification of a StatefulSet. FIELDS: podManagementPolicy <string> #Pod管理策略 replicas <integer> #副本数量 revisionHistoryLimit <integer> #历史版本限制 selector <Object> -required- #选择器，必选项 serviceName <string> -required- #服务名称，必选项 template <Object> -required- #模板，必选项 updateStrategy <Object> #更新策略 volumeClaimTemplates <[]Object> #存储卷申请模板，列表对象形式
如上所述，一个完整的StatefulSet控制器由一个Headless Service、一个StatefulSet和一个volumeClaimTemplate组成。如下资源清单中的定义：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 [root@k8s-master mainfests]# vim stateful-demo.yaml apiVersion: v1 kind: Service metadata: name: myapp-svc labels: app: myapp-svc spec: ports: - port: 80 name: web clusterIP: None selector: app: myapp-pod --- apiVersion: apps/v1 kind: StatefulSet metadata: name: myapp spec: serviceName: myapp-svc replicas: 3 selector: matchLabels: app: myapp-pod template: metadata: labels: app: myapp-pod spec: containers: - name: myapp image: ikubernetes/myapp:v1 ports: - containerPort: 80 name: web volumeMounts: - name: myappdata mountPath: /usr/share/nginx/html volumeClaimTemplates: - metadata: name: myappdata spec: accessModes: ["ReadWriteOnce"] resources: requests: storage: 2Gi
解析上例：由于StatefulSet资源依赖于一个实现存在的Headless类型的Service资源，所以需要先定义一个名为myapp-svc的Headless Service资源，用于为关联到每个Pod资源创建DNS资源记录。接着定义了一个名为myapp的StatefulSet资源，它通过Pod模板创建了3个Pod资源副本，并基于volumeClaimTemplates向前面创建的PV进行了请求大小为2Gi的专用存储卷。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 apiVersion: v1 kind: PersistentVolume metadata: name: pv001 labels: name: pv001 spec: nfs: path: /data/volumes/v1 server: server-n1 accessModes: ["ReadWriteMany","ReadWriteOnce"] capacity: storage: 1Gi --- apiVersion: v1 kind: PersistentVolume metadata: name: pv002 labels: name: pv002 spec: nfs: path: /data/volumes/v2 server: server-n1 accessModes: ["ReadWriteOnce"] capacity: storage: 2Gi --- apiVersion: v1 kind: PersistentVolume metadata: name: pv003 labels: name: pv003 spec: nfs: path: /data/volumes/v3 server: server-n1 accessModes: ["ReadWriteMany","ReadWriteOnce"] capacity: storage: 2Gi --- apiVersion: v1 kind: PersistentVolume metadata: name: pv004 labels: name: pv004 spec: nfs: path: /data/volumes/v4 server: server-n1 accessModes: ["ReadWriteMany","ReadWriteOnce"] capacity: storage: 2Gi --- apiVersion: v1 kind: PersistentVolume metadata: name: pv005 labels: name: pv005 spec: nfs: path: /data/volumes/v5 server: server-n1 accessModes: ["ReadWriteMany","ReadWriteOnce"] capacity: storage: 2Gi
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 [root@k8s-master mainfests]# kubectl apply -f stateful-demo.yaml service/myapp-svc created statefulset.apps/myapp created [root@k8s-master mainfests]# kubectl get svc #查看创建的无头服务myapp-svc NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 50d myapp-svc ClusterIP None <none> 80/TCP 38s [root@k8s-master mainfests]# kubectl get sts #查看statefulset NAME DESIRED CURRENT AGE myapp 3 3 55s [root@k8s-master mainfests]# kubectl get pvc #查看pvc绑定 NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE myappdata-myapp-0 Bound pv002 2Gi RWO 1m myappdata-myapp-1 Bound pv003 2Gi RWO,RWX 1m myappdata-myapp-2 Bound pv004 2Gi RWO,RWX 1m [root@k8s-master mainfests]# kubectl get pv #查看pv绑定 NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE pv001 1Gi RWO,RWX Retain Available 6m pv002 2Gi RWO Retain Bound default/myappdata-myapp-0 6m pv003 2Gi RWO,RWX Retain Bound default/myappdata-myapp-1 6m pv004 2Gi RWO,RWX Retain Bound default/myappdata-myapp-2 6m pv005 2Gi RWO,RWX Retain Available 6m [root@k8s-master mainfests]# kubectl get pods #查看Pod信息 NAME READY STATUS RESTARTS AGE myapp-0 1/1 Running 0 2m myapp-1 1/1 Running 0 2m myapp-2 1/1 Running 0 2m pod-vol-demo 2/2 Running 0 1d redis-5b5d6fbbbd-q8ppz 1/1 Running 1 2d
当删除的时候是从myapp-2开始进行删除的，关闭是逆向关闭
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 [root@k8s-master mainfests]# kubectl delete -f stateful-demo.yaml service "myapp-svc" deleted statefulset.apps "myapp" deleted [root@k8s-master ~]# kubectl get pods -w NAME READY STATUS RESTARTS AGE filebeat-ds-hxgdx 1/1 Running 1 33d filebeat-ds-s466l 1/1 Running 2 33d myapp-0 1/1 Running 0 3m myapp-1 1/1 Running 0 3m myapp-2 1/1 Running 0 3m pod-vol-demo 2/2 Running 0 1d redis-5b5d6fbbbd-q8ppz 1/1 Running 1 2d myapp-0 1/1 Terminating 0 3m myapp-2 1/1 Terminating 0 3m myapp-1 1/1 Terminating 0 3m myapp-1 0/1 Terminating 0 3m myapp-0 0/1 Terminating 0 3m myapp-2 0/1 Terminating 0 3m myapp-1 0/1 Terminating 0 3m myapp-1 0/1 Terminating 0 3m myapp-0 0/1 Terminating 0 4m myapp-0 0/1 Terminating 0 4m myapp-2 0/1 Terminating 0 3m myapp-2 0/1 Terminating 0 3m 此时PVC依旧存在的，再重新创建pod时，依旧会重新去绑定原来的pvc [root@k8s-master mainfests]# kubectl apply -f stateful-demo.yaml service/myapp-svc created statefulset.apps/myapp created [root@k8s-master mainfests]# kubectl get pvc NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE myappdata-myapp-0 Bound pv002 2Gi RWO 5m myappdata-myapp-1 Bound pv003 2Gi RWO,RWX 5m myappdata-myapp-2 Bound pv004 2Gi RWO,RWX 5m
滚动更新
RollingUpdate 更新策略在 StatefulSet 中实现 Pod 的自动滚动更新。 当StatefulSet的 .spec.updateStrategy.type 设置为 RollingUpdate 时，默认为：RollingUpdate。StatefulSet 控制器将在 StatefulSet 中删除并重新创建每个 Pod。 它将以与 Pod 终止相同的顺序进行（从最大的序数到最小的序数），每次更新一个 Pod。 在更新其前身之前，它将等待正在更新的 Pod 状态变成正在运行并就绪。如下操作的滚动更新是有2-0的顺序更新。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 [root@k8s-master mainfests]# vim stateful-demo.yaml #修改image版本为v2 ..... image: ikubernetes/myapp:v2 .... [root@k8s-master mainfests]# kubectl apply -f stateful-demo.yaml service/myapp-svc unchanged statefulset.apps/myapp configured [root@k8s-master ~]# kubectl get pods -w #查看滚动更新的过程 NAME READY STATUS RESTARTS AGE myapp-0 1/1 Running 0 36m myapp-1 1/1 Running 0 36m myapp-2 1/1 Running 0 36m myapp-2 1/1 Terminating 0 36m myapp-2 0/1 Terminating 0 36m myapp-2 0/1 Terminating 0 36m myapp-2 0/1 Terminating 0 36m myapp-2 0/1 Pending 0 0s myapp-2 0/1 Pending 0 0s myapp-2 0/1 ContainerCreating 0 0s myapp-2 1/1 Running 0 2s myapp-1 1/1 Terminating 0 36m myapp-1 0/1 Terminating 0 36m myapp-1 0/1 Terminating 0 36m myapp-1 0/1 Terminating 0 36m myapp-1 0/1 Pending 0 0s myapp-1 0/1 Pending 0 0s myapp-1 0/1 ContainerCreating 0 0s myapp-1 1/1 Running 0 1s myapp-0 1/1 Terminating 0 37m myapp-0 0/1 Terminating 0 37m myapp-0 0/1 Terminating 0 37m myapp-0 0/1 Terminating 0 37m
在创建的每一个Pod中，每一个pod自己的名称都是可以被解析的，如下：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 [root@k8s-master ~]# kubectl get pods -o wide NAME READY STATUS RESTARTS AGE IP NODE myapp-0 1/1 Running 0 8m 10.244.1.62 k8s-node01 myapp-1 1/1 Running 0 8m 10.244.2.49 k8s-node02 myapp-2 1/1 Running 0 8m 10.244.1.61 k8s-node01 [root@k8s-master mainfests]# kubectl exec -it myapp-0 -- /bin/sh / # nslookup myapp-0.myapp-svc.default.svc.cluster.local nslookup: can't resolve '(null)': Name does not resolve Name: myapp-0.myapp-svc.default.svc.cluster.local Address 1: 10.244.1.62 myapp-0.myapp-svc.default.svc.cluster.local / # nslookup myapp-1.myapp-svc.default.svc.cluster.local nslookup: can't resolve '(null)': Name does not resolve Name: myapp-1.myapp-svc.default.svc.cluster.local Address 1: 10.244.2.49 myapp-1.myapp-svc.default.svc.cluster.local / # nslookup myapp-2.myapp-svc.default.svc.cluster.local nslookup: can't resolve '(null)': Name does not resolve Name: myapp-2.myapp-svc.default.svc.cluster.local Address 1: 10.244.1.61 myapp-2.myapp-svc.default.svc.cluster.local 从上面的解析，我们可以看到在容器当中可以通过对Pod的名称进行解析到ip。其解析的域名格式如下： pod_name.service_name.ns_name.svc.cluster.local eg: myapp-0.myapp.default.svc.cluster.local
扩展伸缩 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 [root@k8s-master mainfests]# kubectl scale sts myapp --replicas=4 #扩容副本增加到4个 statefulset.apps/myapp scaled [root@k8s-master ~]# kubectl get pods -w #动态查看扩容 NAME READY STATUS RESTARTS AGE myapp-0 1/1 Running 0 23m myapp-1 1/1 Running 0 23m myapp-2 1/1 Running 0 23m myapp-3 0/1 Pending 0 0s myapp-3 0/1 Pending 0 0s myapp-3 0/1 ContainerCreating 0 0s myapp-3 1/1 Running 0 1s [root@k8s-master mainfests]# kubectl get pv #查看pv绑定 NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE pv001 1Gi RWO,RWX Retain Available 1h pv002 2Gi RWO Retain Bound default/myappdata-myapp-0 1h pv003 2Gi RWO,RWX Retain Bound default/myappdata-myapp-1 1h pv004 2Gi RWO,RWX Retain Bound default/myappdata-myapp-2 1h pv005 2Gi RWO,RWX Retain Bound default/myappdata-myapp-3 1h [root@k8s-master mainfests]# kubectl patch sts myapp -p '{"spec":{"replicas":2}}' #打补丁方式缩容 statefulset.apps/myapp patched [root@k8s-master ~]# kubectl get pods -w #动态查看缩容 NAME READY STATUS RESTARTS AGE myapp-0 1/1 Running 0 25m myapp-1 1/1 Running 0 25m myapp-2 1/1 Running 0 25m myapp-3 1/1 Running 0 1m myapp-3 1/1 Terminating 0 2m myapp-3 0/1 Terminating 0 2m myapp-3 0/1 Terminating 0 2m myapp-3 0/1 Terminating 0 2m myapp-2 1/1 Terminating 0 26m myapp-2 0/1 Terminating 0 26m myapp-2 0/1 Terminating 0 27m myapp-2 0/1 Terminating 0 27m
更新策略和版本升级
修改更新策略，以partition方式进行更新，更新值为2，只有myapp编号大于等于2的才会进行更新。类似于金丝雀部署方式。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 [root@k8s-master mainfests]# kubectl patch sts myapp -p '{"spec":{"updateStrategy":{"rollingUpdate":{"partition":2}}}}' statefulset.apps/myapp patched [root@k8s-master ~]# kubectl get sts myapp NAME DESIRED CURRENT AGE myapp 4 4 1h [root@k8s-master ~]# kubectl describe sts myapp Name: myapp Namespace: default CreationTimestamp: Wed, 10 Oct 2018 21:58:24 -0400 Selector: app=myapp-pod Labels: <none> Annotations: kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"apps/v1","kind":"StatefulSet","metadata":{"annotations":{},"name":"myapp","namespace":"default"},"spec":{"replicas":3,"selector":{"match... Replicas: 4 desired | 4 total Update Strategy: RollingUpdate Partition: 2 ......
目前副本是2，将image的版本升级为v3，此时不会进行升级更新，可以查看myapp-0和myapp-1的镜像仍为v2，副本改为3后，myapp-2的镜像为v3，myapp-0和myapp-1的镜像仍为v2。这样就实现了金丝雀发布的效果。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 [root@k8s-master mainfests]# kubectl set image sts/myapp myapp=ikubernetes/myapp:v3 statefulset.apps/myapp image updated [root@k8s-master ~]# kubectl get sts -o wide NAME DESIRED CURRENT AGE CONTAINERS IMAGES myapp 4 4 1h myapp ikubernetes/myapp:v3 [root@k8s-master ~]# kubectl get pods myapp-1 -o yaml |grep image - image: ikubernetes/myapp:v2 imagePullPolicy: IfNotPresent image: ikubernetes/myapp:v2 imageID: docker-pullable://ikubernetes/myapp@sha256:85a2b81a62f09a414ea33b74fb8aa686ed9b168294b26b4c819df0be0712d358 [root@k8s-master mainfests]# kubectl scale sts myapp --replicas=3 [root@k8s-master ~]# kubectl get pods myapp-2 -o yaml |grep image - image: ikubernetes/myapp:v3 imagePullPolicy: IfNotPresent image: ikubernetes/myapp:v3 imageID: docker-pullable://ikubernetes/myapp@sha256:b8d74db2515d3c1391c78c5768272b9344428035ef6d72158fd9f6c4239b2c69
将剩余的Pod也更新版本，只需要将更新策略的partition值改为0即可，如下：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 [root@k8s-master mainfests]# kubectl patch sts myapp -p '{"spec":{"updateStrategy":{"rollingUpdate":{"partition":0}}}}' statefulset.apps/myapp patched [root@k8s-master ~]# kubectl get pods -w NAME READY STATUS RESTARTS AGE myapp-0 1/1 Running 0 58m myapp-1 1/1 Running 0 58m myapp-2 1/1 Running 0 13m myapp-3 1/1 Running 0 13m myapp-1 1/1 Terminating 0 58m myapp-1 0/1 Terminating 0 58m myapp-1 0/1 Terminating 0 58m myapp-1 0/1 Terminating 0 58m myapp-1 0/1 Pending 0 0s myapp-1 0/1 Pending 0 0s myapp-1 0/1 ContainerCreating 0 0s myapp-1 1/1 Running 0 2s myapp-0 1/1 Terminating 0 58m myapp-0 0/1 Terminating 0 58m myapp-0 0/1 Terminating 0 58m myapp-0 0/1 Terminating 0 58m myapp-0 0/1 Pending 0 0s myapp-0 0/1 Pending 0 0s myapp-0 0/1 ContainerCreating 0 0s myapp-0 1/1 Running 0 2s
参考资料