一點題外話：kubernetes官方3月25號釋出1.14，本文28號完成。1.14升級安裝中文指南，目前全網大概最新吧，支援請賞個贊。
升級準備
本次升級主要參考官方Upgrading kubeadm clusters from v1.13 to v1.14
升級之前注意事項(翻譯自官方文件)：
- 1.13.0以上，使用kubeadm部署的kubernetes叢集
- Swap分割槽需要disabled
- 叢集的控制平面個數和etcd pods需要是確定的。
- 認真閱讀release notes。
- 備份。主要是備份一些重要的元件，比如database等。雖然升級不會調整業務負載，僅僅調整kubernetes，但是備份總是沒錯的。
- 所有的容器都會被重啟，因為hash值會變化。
- 只能夠進行小版本的升級，並且升級過程不能夠跳級，比如從1.y到1.y+1,而不能夠從1.y到1.y+2
按照要求檢視kubernetes 1.14 更改說明重點閱讀Urgent Upgrade Notes，結合自己業務，並沒有發現特別重大的變動，可以放心升級。
kubernetes叢集是按照kubernetes 1.13 全新安裝指南搭建，如下:
[hall@192-168-10-21 ~]$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
192-168-10-14 Ready master 36h v1.13.0
192-168-10-18 Ready <none> 103d v1.13.0
192-168-10-21 Ready master 104d v1.13.0
複製程式碼業務資料備份，就不用介紹了。實際上安全起見最好先在測試叢集上進行升級，通過後再考慮正式叢集的升級。
升級過程主要變化的是kubernetes系統服務，重點是kubelet，所以將kubelet配置備份一下更為穩妥，方法如下：
1 檢視kubelet服務配置:
[root@192-168-10-94 ~]# systemctl status kubelet
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/etc/systemd/system/kubelet.service; enabled; vendor preset: disabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: active (running) since 二 2019-03-19 18:38:46 CST; 1 weeks 1 days ago
Docs: https://kubernetes.io/docs/
Main PID: 6033 (kubelet)
Tasks: 17
Memory: 59.1M
CGroup: /system.slice/kubelet.service
└─6033 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --cgroup-driver=cgroupfs --network-plugin=cni --pod-infra-container-image=re...
複製程式碼2 檢視服務的配置檔案 10-kubeadm.conf :
[root@192-168-10-94 ~]# cat /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
# Note: This dropin only works with kubeadm and kubelet v1.11+
[Service]
Environment="KUBELET_KUBECONFIG_ARGS=--bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf"
Environment="KUBELET_CONFIG_ARGS=--config=/var/lib/kubelet/config.yaml"
# This is a file that "kubeadm init" and "kubeadm join" generates at runtime, populating the KUBELET_KUBEADM_ARGS variable dynamically
EnvironmentFile=-/var/lib/kubelet/kubeadm-flags.env
# This is a file that the user can use for overrides of the kubelet args as a last resort. Preferably, the user should use
# the .NodeRegistration.KubeletExtraArgs object in the configuration files instead. KUBELET_EXTRA_ARGS should be sourced from this file.
EnvironmentFile=-/etc/sysconfig/kubelet
ExecStart=
ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS
複製程式碼3 備份涉及的配置檔案
/etc/kubernetes/bootstrap-kubelet.conf (可能並不存在，沒有也沒有關係)
/etc/kubernetes/kubelet.conf
/var/lib/kubelet/kubeadm-flags.env
/etc/sysconfig/kubelet
複製程式碼下面正式開始升級過程。
升級主控節點
升級之前，一定要確保具有多個控制節點，這樣可以保障叢集的可用。單一控制節點，升級萬一掛了，怕是比較麻煩。新增控制節點的方法，參考上文的kubernetes 1.13 全新安裝指南。
如果沒有特殊說明本文除 kubectl 以外的命令，都是使用 root 賬號執行。
1 先檢查一下repo源中kubeadm是否更新到 1.14.0 的版本
yum list --showduplicates kubeadm --disableexcludes=kubernetes
複製程式碼我本地的源沒有找到 1.14.0 。 使用下面命令清理，後再行檢查可以得到 1.14.0
yum --disablerepo=\* --enablerepo=kubernetes clean all
2 再次檢視kubeadm版本資訊
[root@192-168-10-21 ~]# kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"13", GitVersion:"v1.13.4", GitCommit:"c27b913fddd1a6c480c229191a087698aa92f0b1", GitTreeState:"clean", BuildDate:"2019-02-28T13:35:32Z", GoVersion:"go1.11.5", Compiler:"gc", Platform:"linux/amd64"}
複製程式碼3 安裝kubeadm工具
yum install -y kubeadm-1.14.0-0 --disableexcludes=kubernetes
複製程式碼4 確認kubeadm版本升級完成
[root@192-168-10-21 ~]# kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.0", GitCommit:"641856db18352033a0d96dbc99153fa3b27298e5", GitTreeState:"clean", BuildDate:"2019-03-25T15:51:21Z", GoVersion:"go1.12.1", Compiler:"gc", Platform:"linux/amd64"}
複製程式碼5 升級檢查和方案
[root@192-168-10-21 ~]# kubeadm upgrade plan
[preflight] Running pre-flight checks.
[upgrade] Making sure the cluster is healthy:
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[upgrade] Fetching available versions to upgrade to
[upgrade/versions] Cluster version: v1.13.0
[upgrade/versions] kubeadm version: v1.14.0
Awesome, you're up-to-date! Enjoy!
kubeadm upgrade apply v1.14.0
複製程式碼這裡的提示資訊和官方文件有出入，不過這是正常的資訊。
6 升級kubeadm到1.14
kubeadm upgrade apply v1.14.0
這個執行過程，視叢集情況，大概會執行幾分鐘，輸出資訊也比較多，大概如下:
[root@192-168-10-21 ~]# kubeadm upgrade apply v1.14.0
[preflight] Running pre-flight checks.
[upgrade] Making sure the cluster is healthy:
.....
[upgrade/staticpods] Component "kube-scheduler" upgraded successfully!
[upload-config] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.14" in namespace kube-system with the configuration for the kubelets in the cluster
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.14" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstrap-token] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstrap-token] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy
[upgrade/successful] SUCCESS! Your cluster was upgraded to "v1.14.0". Enjoy!
[upgrade/kubelet] Now that your control plane is upgraded, please proceed with upgrading your kubelets if you haven't already done so.
複製程式碼7 檢查CNI情況，確定是否要升級
kubernetes架構，網路部分確定Container Network Interface介面，具體實現交由其它元件。我的叢集使用flannel，檢查一下：
kubectl get pods -n kube-system
...
kubectl describe pod/kube-flannel-ds-amd64-5xxh7 -n kube-system
...
Image: quay.io/coreos/flannel:v0.11.0-amd64
複製程式碼使用的是 0.11， 檢視flannel主頁得知已經是最新版，這一步不用處理。
8 升級kubectl和kubelet
yum install -y kubelet-1.14.0-0 kubectl-1.14.0-0 --disableexcludes=kubernetes
複製程式碼9 重啟kubelet
[root@192-168-10-21 ~]# systemctl restart kubelet
Warning: kubelet.service changed on disk. Run 'systemctl daemon-reload' to reload units.
[root@192-168-10-21 ~]# systemctl daemon-reload
[root@192-168-10-21 ~]# systemctl restart kubelet
複製程式碼實際上，重啟kubelet失敗，報錯：Failed to start ContainerManager failed to initialise top level QOS containers。 排查過程請見附1
10 檢查升級結果
[hall@192-168-10-21 ~]$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
192-168-10-14 Ready master 38h v1.13.0
192-168-10-18 Ready <none> 103d v1.13.0
192-168-10-21 Ready master 104d v1.14.0
複製程式碼192-168-10-21的狀態為 Ready ，版本也變為 1.14.0 ，主控節點升級成功。
其它控制節點升級
-
參考上文升級好kubeadm，kubectl和kubelet工具。
-
升級到1.14
主控節點已經執行了檢查和升級，192-168-10-14只需要執行 kubeadm upgrade apply v1.14.0。
不幸的是，又遇到了一點狀況 failed to get APIEndpoint information for this node，排查過程請見附2
-
重啟kubelet
-
檢查升級結果
[hall@192-168-10-21 ~]$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
192-168-10-14 Ready master 39h v1.14.0
192-168-10-18 Ready <none> 103d v1.13.0
192-168-10-21 Ready master 104d v1.14.0
複製程式碼業務節點升級
1 臨時備份
因為叢集就一個業務節點，為安全起見，先調整一個控制節點，用於臨時支撐業務：
[tyhall51@192-168-10-21 ~]$ kubectl taint node 192-168-10-14 node-role.kubernetes.io/master-
node/192-168-10-14 untainted
複製程式碼然後業務節點臨時增加汙點，防止升級期間排程：
[tyhall51@192-168-10-21 ~]$ kubectl drain 192-168-10-18 --ignore-daemonsets
node/192-168-10-18 cordoned
error: unable to drain node "192-168-10-18", aborting command...
There are pending nodes to be drained:
192-168-10-18
error: cannot delete Pods with local storage (use --delete-local-data to override): kube-system/elasticsearch-logging-0, kube-system/elasticsearch-logging-1, kube-system/monitoring-influxdb-8b7d57f5c-2bhlw
複製程式碼2 安裝kubeadm工具
3 升級kubedam到1.14
[root@192-168-10-18 ~]# kubeadm upgrade node config --kubelet-version v1.14.0
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.14" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[upgrade] The configuration for this node was successfully updated!
[upgrade] Now you should go ahead and upgrade the kubelet package using your package manager.
複製程式碼4 升級kubectl和kubelet
kubelet同樣需要重啟
5 還原臨時備份
先取消業務節點汙點
[tyhall51@192-168-10-21 ~]$ kubectl uncordon 192-168-10-18
node/192-168-10-18 uncordoned
複製程式碼然後還原master節點
[tyhall51@192-168-10-21 ~]$ kubectl taint node 192-168-10-14 node-role.kubernetes.io/master=:NoSchedule
node/192-168-10-14 tainted
複製程式碼6 檢查結果
[tyhall51@192-168-10-21 ~]$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
192-168-10-14 Ready master 40h v1.14.0
192-168-10-18 Ready <none> 103d v1.14.0
192-168-10-21 Ready master 104d v1.14.0
複製程式碼以上，完成了kubernetes從1.13到1.14的升級，整體上講，升級過程比較輕鬆。總結一下升級過程:
- 詳細閱讀升級指南，完成重要業務資訊備份，完成kubelet配置。
- 升級主要控制節點。
- 升級其它控制節點。
- 升級業務節點。
附
- kubelet重啟失敗
kubelet重啟失敗，systemctl status kubelet 中錯誤資訊：
Failed to start ContainerManager failed to initialise top level QOS containers
複製程式碼參考https://github.com/kubernetes/kubernetes/issues/43704提示在kubelet啟動時候增加 --cgroups-per-qos=false --enforce-node-allocatable="" 即可解決。之前備份kubelet的配置時候知道 /var/lib/kubelet/kubeadm-flags.env 中定義kubelet的啟動引數，在其中加上，重啟kubelet，恢復正常。
- kubeadm 升級失敗
[root@192-168-10-14 ~]# kubeadm upgrade apply v1.14.0
[preflight] Running pre-flight checks.
[upgrade] Making sure the cluster is healthy:
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[upgrade/config] FATAL: failed to getAPIEndpoint: failed to get APIEndpoint information for this node
複製程式碼根據提示，使用編輯 kubectl -n kube-system edit cm kubeadm-config -oyaml kubeadm-config, 調整apiEndpoints為:
apiEndpoints:
192-168-10-21:
advertiseAddress: 192.168.10.21
bindPort: 6443
192-168-10-14:
advertiseAddress: 192.168.10.14
bindPort: 6443
複製程式碼繼續執行kubeadm upgrade apply v1.14.0，正常完成。