k8s deployment的滾動(dòng)更新

一、知識(shí)準(zhǔn)備

● 本文詳細(xì)探索deployment在滾動(dòng)更新時(shí)候的行為

二、環(huán)境準(zhǔn)備

組件版本

OS	Ubuntu 18.04.1 LTS
docker	18.06.0-ce

三、準(zhǔn)備鏡像

首先準(zhǔn)備2個(gè)不同版本的鏡像，用于測(cè)試（已經(jīng)在阿里云上創(chuàng)建好2個(gè)不同版本的nginx鏡像）

docker pull registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v1 docker pull registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v2 root@k8s-master:~# docker run -d --rm -p 10080:80 nginx:v1 e88097841c5feef92e4285a2448b943934ade5d86412946bc8d86e262f80a050 root@k8s-master:~# curl http://127.0.0.1:10080 ---------- version: v1 hostname: f5189a5d3ad3

四、deployment、replicaset、pod之間的關(guān)系

+------------+| deployment |+-----+------+||||+--------------------------------------------------+| | || | || | || | || | || | | +------v------+ +------v------+ +------v------+ |replicaset:v1| |replicaset:v2| |replicaset:v3| +-------------+ +------+------+ +-------------+||+--------+---------+| || |+---v---+ +---v---+|pod:v2 | |pod:v2 |+-------+ +-------+

● deployment調(diào)度replicaset，pod由replicaset調(diào)度
● deployment管理多個(gè)replicaset版本，可用于回滾
● replicaset控制pod的行為，包括新增pod、刪除pod

我們首先準(zhǔn)備一個(gè)yaml文件用于測(cè)試：

root@k8s-master:~# more roll_update.yaml apiVersion: extensions/v1beta1 kind: Deployment metadata:name: image-deployment spec:replicas: 1template:metadata:labels:app: image-updatespec:containers:- name: nginximage: registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v1imagePullPolicy: Always

---

簡(jiǎn)單驗(yàn)證一下：

root@k8s-master:~# kubectl apply -f roll_update.yaml deployment.extensions "update-deployment" created root@k8s-master:~# kubectl get deploy NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE update-deployment 3 3 3 3 54s root@k8s-master:~# kubectl get rs NAME DESIRED CURRENT READY AGE update-deployment-7db77f7cc6 3 3 3 56s root@k8s-master:~# kubectl get pod NAME READY STATUS RESTARTS AGE update-deployment-7db77f7cc6-7j49g 1/1 Running 0 1m update-deployment-7db77f7cc6-b75wn 1/1 Running 0 1m update-deployment-7db77f7cc6-cfnt5 1/1 Running 0 1m

deployment、replicaset、pod都已經(jīng)正常啟動(dòng)，下面分析一下他們的行為：

deployment

root@k8s-master:~# kubectl describe deploy update-deployment Name: update-deployment Namespace: default ... Replicas: 3 desired | 3 updated | 3 total | 3 available | 0 unavailable StrategyType: RollingUpdate MinReadySeconds: 0 RollingUpdateStrategy: 1 max unavailable, 1 max surge ... NewReplicaSet: update-deployment-7db77f7cc6 (3/3 replicas created) Events:Type Reason Age From Message---- ------ ---- ---- -------Normal ScalingReplicaSet 1m deployment-controller Scaled up replica set update-deployment-7db77f7cc6 to 3

● deployment創(chuàng)建了一個(gè)replicaset，叫做update-deployment-7db77f7cc6（7db77f7cc6是replicaset的template hash值）
● 根據(jù)配置文件的要求，replicaset的副本數(shù)為3

---

replicaset

root@k8s-master:~# kubectl describe rs update-deployment-7db77f7cc6 Name: update-deployment-7db77f7cc6 Namespace: default ... Controlled By: Deployment/update-deployment Replicas: 3 current / 3 desired Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed ... Events:Type Reason Age From Message---- ------ ---- ---- -------Normal SuccessfulCreate 3m replicaset-controller Created pod: update-deployment-7db77f7cc6-7j49gNormal SuccessfulCreate 3m replicaset-controller Created pod: update-deployment-7db77f7cc6-b75wnNormal SuccessfulCreate 3m replicaset-controller Created pod: update-deployment-7db77f7cc6-cfnt5

● replicaset創(chuàng)建了3個(gè)pod

---

pod

root@k8s-master:~# kubectl describe pod update-deployment-7db77f7cc6-7j49g Name: update-deployment-7db77f7cc6-7j49g Namespace: default ... Status: Running IP: 10.10.169.140 Controlled By: ReplicaSet/update-deployment-7db77f7cc6 ... Events:Type Reason Age From Message---- ------ ---- ---- -------Normal Scheduled 9m default-scheduler Successfully assigned update-deployment-7db77f7cc6-7j49g to k8s-node2Normal SuccessfulMountVolume 9m kubelet, k8s-node2 MountVolume.SetUp succeeded for volume "default-token-v9nkm"Normal Pulling 9m kubelet, k8s-node2 pulling image "registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v1"Normal Pulled 9m kubelet, k8s-node2 Successfully pulled image "registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v1"Normal Created 9m kubelet, k8s-node2 Created containerNormal Started 9m kubelet, k8s-node2 Started container

● pod被replicaset創(chuàng)建之后，開始分配到worker節(jié)點(diǎn)、拉取鏡像、啟動(dòng)容器等一系列操作
● 所以pod的命名方式是：update-deployment-7db77f7cc6-7j49g（deployment名字-replicaset模板hash名字-pod模板hash名字）

---

不禁有同學(xué)要問，為什么搞這么復(fù)雜，啟動(dòng)一個(gè)pod需要?jiǎng)佑眠@么多組件呢？下面用一個(gè)場(chǎng)景說明為啥需要這么多組件：

鏡像版本更新

● 當(dāng)鏡像版本有更新時(shí)（三種方法都可以實(shí)現(xiàn)，參考前一篇文章：更新k8s鏡像版本的三種方式），既要保證服務(wù)可用，又要保證在線更新，流程應(yīng)該是：
??1、先增加一個(gè)pod，鏡像版本為新版本
??2、pod可用之后，刪除一個(gè)老版本pod
??3、循環(huán)第1、2步，直到老版本pod全部刪除，新版本的pod全部可用
● 上述的這個(gè)過程就是replicaset的作用，它根據(jù)需求，自動(dòng)的增加新版本pod，然后刪除老版本pod，直到老版本pod全部刪除，新版本的pod全部可用
● 如果此時(shí)版本需要回退，那replicaset需要把剛才的步驟逆向更新一遍，實(shí)現(xiàn)版本回退
● deployment的作用就是管理replicaset。deployment會(huì)保存各個(gè)版本的replicaset，一旦需要進(jìn)行版本回滾，deployment會(huì)立即回滾replicaset的版本，從而控制pod狀態(tài)

---

下面測(cè)試一下：

使用patch命令更新鏡像版本，并且使用pause命令來觀察：

root@k8s-master:~# kubectl patch deployment update-deployment \ --patch '{"spec": {"template": {"spec": {"containers": [{"name": "nginx","image":"registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v2"}]}}}}' \ && kubectl rollout pause deployment update-deployment deployment.extensions "update-deployment" patched deployment.apps "update-deployment" paused

此時(shí)pod狀態(tài)：

root@k8s-master:~# kubectl get pod -owide NAME READY STATUS RESTARTS AGE IP NODE update-deployment-7db77f7cc6-7j49g 1/1 Running 0 1h 10.10.169.140 k8s-node2 update-deployment-7db77f7cc6-b75wn 1/1 Running 0 1h 10.10.235.211 k8s-master update-deployment-7db77f7cc6-cfnt5 1/1 Terminating 0 1h 10.10.36.126 k8s-node1 update-deployment-7fb7b4b557-6987x 1/1 Running 0 7s 10.10.36.127 k8s-node1 update-deployment-7fb7b4b557-dxdqb 1/1 Running 0 10s 10.10.169.139 k8s-node2

新增了2個(gè)pod，而刪除了1個(gè)老版本的pod

此時(shí)replicaset狀態(tài)：

root@k8s-master:~# kubectl get rs -owide NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR update-deployment-7db77f7cc6 2 2 2 1h nginx registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v1 app=roll-update,pod-template-hash=3863393772 update-deployment-7fb7b4b557 2 2 2 4m nginx registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v2 app=roll-update,pod-template-hash=3963606113

有一個(gè)新版本的replicaset創(chuàng)建了出來，并且需求的pod數(shù)量為2，而原來的replicaset需求的pod數(shù)量從3降為2

查看replicaset版本：

root@k8s-master:~# kubectl rollout history deploy update-deployment deployments "update-deployment" REVISION CHANGE-CAUSE 1 <none> 2 update version to v2

新增了一個(gè)版本2

由于使用pause命令，更新過程到此會(huì)卡主，我們讓更新的過程繼續(xù)下去：

root@k8s-master:~# kubectl rollout resume deployment update-deployment deployment.apps "update-deployment" resumed

查看狀態(tài)：

root@k8s-master:~# kubectl get pod NAME READY STATUS RESTARTS AGE update-deployment-7fb7b4b557-6987x 1/1 Running 0 15m update-deployment-7fb7b4b557-dxdqb 1/1 Running 0 15m update-deployment-7fb7b4b557-wg5c8 1/1 Running 0 1m root@k8s-master:~# kubectl get rs -owide NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR update-deployment-7db77f7cc6 0 0 0 1h nginx registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v1 app=roll-update,pod-template-hash=3863393772 update-deployment-7fb7b4b557 3 3 3 14m nginx registry.cn-beijing.aliyuncs.com/mrvolleyball/nginx:v2 app=roll-update,pod-template-hash=3963606113

v1版本的replicaset已經(jīng)沒有pod，但是歷史記錄還是保留的，可以通過deployment調(diào)度快速回滾

五、小結(jié)

● 本文介紹了deployment滾動(dòng)更新時(shí)，deployment、replicaset、pod的細(xì)節(jié)以及創(chuàng)建過程
● 介紹了deployment版本管理的方式

參考鏈接：https://www.cnblogs.com/wangkun122/articles/12707216.html

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