在前面一篇中提到过ReplicaSet，而ReplicaSet很多时候是无法满足现状，ReplicaSet确保在任何给定时间运行指定数量的pod副本。但是，Deployment是一个更高级别的概念replicaset本身仅仅并不是直接被控制，在replicaset之上是由Deployment来控制，Deployment通过控制replicaset来控制pod。Deployment支持扩缩容，滚动更新，回滚等，并且提供声明式配置功能，可随时声明，声明后可改变apiserver上期望的目标状态。只需要支持动态资源修改！Deployment善于管控无状态应用（关注群体，不关注个体）
在Deployment中，Deployment控制两个(replicaset)rs，刚开始在v1 rs删除一个，并在v2 rs新建一个，紧接着在v1 在删除一个，在v2在创建一个，直到将v1全部迁移到v2上。如果想滚回v1，也可。如下图：
不但如此，Deployment可以控制更新节奏和更新逻辑来实现更新场景。如：灰度，蓝绿，金丝雀
如上图所示，倘若3个pod正好符合当前业务场景负载，此刻删除则会影响，那么就需要临时加一个pod，而后在删除一个。以最多多少个，最少多少个进行控制。
explain
strategy : 定义更新策略 Recreate： 重建更新（删掉就重建，依次重复） rollingUpdate：滚动更新如果type等于RollingUpdate,则可以使用RollingUpdate来进行定义如果type等于Recreate，则RollingUpdate失效查看详情
[root@linuxea linuxea]# kubectl describe deploy dpment-linuxea
Name: dpment-linuxea
Namespace: default
CreationTimestamp: Fri, 31 Aug 2018 14:23:33 +0100
Labels: <none>
Annotations: deployment.kubernetes.io/revision=1
kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"name":"dpment-linuxea","namespace":"default"},"spec":{"replicas":3,"selector"...
Selector: app=linuxea_app,version=v0.1.32
Replicas: 3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 25% max unavailable, 25% max surgeRollingUpdate可控制更新粒度 maxSurge: 对应的更新过程当中，最多能超出指定目标数 取值方式：数量和百分比（如：原本5个，20%就是1个，40%就是2个）maxUnavilable：最多有几个不可用(如：原本5个，最多有1个不可用，那就意味着，最少有4个可用)revisionHistoryLimit：在滚动更新后，保存多少个历史版本，默认10个，设置为0不保存 paused : 暂停，不更新其中，replica sets上下共有三级结构，如下：
apply声明创建
[root@linuxea linuxea]# cat deploy-demt.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: dpment-linuxea
namespace: default
spec:
replicas: 3
selector:
matchLabels:
app: linuxea_app
version: v0.1.32
template:
metadata:
labels:
app: linuxea_app
version: v0.1.32
spec:
containers:
- name: nginx-a
image: marksugar/nginx:1.14.b
ports:
- name: http
containerPort: 80创建
[root@linuxea linuxea]# kubectl apply -f deploy-demt.yaml
deployment.apps/dpment-linuxea created[root@linuxea linuxea]# kubectl get deploy
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
dpment-linuxea 2 2 2 2 31s[root@linuxea linuxea]# kubectl get rs
NAME DESIRED CURRENT READY AGE
dpment-linuxea-65b8d94cc6 2 2 2 45s在dpment-linuxea-65b8d94cc6中的65b8d94cc6是模板的哈希值(且每一个模板的哈希值都不一样)，dpment-linuxea是name
而在pod中的name段dpment-linuxea-65b8d94cc6-q7hw8，dpment-linuxea-65b8d94cc6-已经作为前缀
[root@linuxea linuxea]# kubectl get pods
NAME READY STATUS RESTARTS AGE
client-linuxea 1/1 Running 0 7d
dpment-linuxea-65b8d94cc6-q7hw8 1/1 Running 0 3m
dpment-linuxea-65b8d94cc6-tvn2d 1/1 Running 0 3m倘若现在想扩展，直接修改yaml文件（直接vim打开，为了清楚的记录我修改的值，直接sed）
[root@linuxea linuxea]# sed -i 's/replicas: 2/replicas: 3/g' deploy-demt.yamlapply是可以执行多次的。每次的变化会同步到etcd，apiserver发现与etcd不同，更新状态现有状态到预期状态。
[root@linuxea linuxea]# kubectl apply -f deploy-demt.yaml
deployment.apps/dpment-linuxea configured[root@linuxea linuxea]# kubectl get rs
NAME DESIRED CURRENT READY AGE
dpment-linuxea-65b8d94cc6 3 3 3 10m
linuxea.com 5 5 5 1d
nginx-linuxea-5786698598 3 3 3 5d[root@linuxea linuxea]# kubectl get deploy
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
dpment-linuxea 3 3 3 3 10m
nginx-linuxea 3 3 3 3 5d[root@linuxea linuxea]# kubectl get pods
NAME READY STATUS RESTARTS AGE
client-linuxea 1/1 Running 0 7d
dpment-linuxea-65b8d94cc6-kcckt 1/1 Running 0 23s
dpment-linuxea-65b8d94cc6-q7hw8 1/1 Running 0 11m
dpment-linuxea-65b8d94cc6-tvn2d 1/1 Running 0 11m查看详情kubectl describe deploy dpment-linuxea,其中StrategyType默认为RollingUpdate
[root@linuxea linuxea]# kubectl describe deploy dpment-linuxea
Name: dpment-linuxea
Namespace: default
CreationTimestamp: Fri, 31 Aug 2018 14:23:33 +0100
Labels: <none>
Annotations: deployment.kubernetes.io/revision=1
kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"name":"dpment-linuxea","namespace":"default"},"spec":{"replicas":3,"selector"...
Selector: app=linuxea_app,version=v0.1.32
Replicas: 3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 25% max unavailable, 25% max surge如上，RollingUpdateStrategy: 25% max unavailable, 25% max surge可以使用 kubectl get pods -l app=linuxea_app -w关注到整个过程为了看到效果，在修改一次image
[root@linuxea linuxea]# sed -i 's/nginx:1.14.a/nginx:1.14.b/'g deploy-demt.yaml[root@linuxea linuxea]# kubectl apply -f deploy-demt.yaml
deployment.apps/dpment-linuxea configuredkubectl get pods -l app=linuxea_app -w观察自动滚动更新的过程
[root@linuxea linuxea]# kubectl get pods -l app=linuxea_app -w
NAME READY STATUS RESTARTS AGE
dpment-linuxea-65b8d94cc6-kcckt 1/1 Running 0 16m
dpment-linuxea-65b8d94cc6-q7hw8 1/1 Running 0 27m
dpment-linuxea-65b8d94cc6-tvn2d 1/1 Running 0 27m
dpment-linuxea-648d599b5f-xh7xp 0/1 Pending 0 0s
dpment-linuxea-648d599b5f-xh7xp 0/1 Pending 0 0s
dpment-linuxea-648d599b5f-xh7xp 0/1 ContainerCreating 0 0s
dpment-linuxea-648d599b5f-xh7xp 1/1 Running 0 1s
dpment-linuxea-65b8d94cc6-kcckt 1/1 Terminating 0 18m
dpment-linuxea-648d599b5f-94pd2 0/1 Pending 0 0s
dpment-linuxea-648d599b5f-94pd2 0/1 Pending 0 0s
dpment-linuxea-648d599b5f-94pd2 0/1 ContainerCreating 0 0s
dpment-linuxea-648d599b5f-94pd2 1/1 Running 0 1s
dpment-linuxea-65b8d94cc6-tvn2d 1/1 Terminating 0 29m
dpment-linuxea-648d599b5f-blrzr 0/1 Pending 0 0s
dpment-linuxea-648d599b5f-blrzr 0/1 Pending 0 0s
dpment-linuxea-648d599b5f-blrzr 0/1 ContainerCreating 0 0s
dpment-linuxea-648d599b5f-blrzr 1/1 Running 0 2s
dpment-linuxea-65b8d94cc6-q7hw8 1/1 Terminating 0 29m
dpment-linuxea-65b8d94cc6-kcckt 0/1 Terminating 0 19m
dpment-linuxea-65b8d94cc6-kcckt 0/1 Terminating 0 19m
dpment-linuxea-65b8d94cc6-kcckt 0/1 Terminating 0 19m
dpment-linuxea-65b8d94cc6-tvn2d 0/1 Terminating 0 30m
dpment-linuxea-65b8d94cc6-q7hw8 0/1 Terminating 0 30m
dpment-linuxea-65b8d94cc6-tvn2d 0/1 Terminating 0 30m
dpment-linuxea-65b8d94cc6-tvn2d 0/1 Terminating 0 30m
dpment-linuxea-65b8d94cc6-q7hw8 0/1 Terminating 0 30m
dpment-linuxea-65b8d94cc6-q7hw8 0/1 Terminating 0 30mPending表示尚未调度完成，完成则会创建，依次重复更新完成结束
- 历史版本信息
当，使用kubectl get rs -o wide会发现，此前创建的dpment-linuxea-65b8d94cc6 依然存在。DESIRED却为0
[root@linuxea linuxea]# kubectl get rs -o wide
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
dpment-linuxea-648d599b5f 3 3 3 3m nginx-a marksugar/nginx:1.14.b app=linuxea_app,pod-template-hash=2048155619,version=v0.1.32
dpment-linuxea-65b8d94cc6 0 0 0 33m nginx-a marksugar/nginx:1.14.a app=linuxea_app,pod-template-hash=2164850772,version=v0.1.32也可查看历史
[root@linuxea linuxea]# kubectl rollout history deployment dpment-linuxea
deployments "dpment-linuxea"
REVISION CHANGE-CAUSE
1 <none>
2 <none>
[root@linuxea linuxea]# patch补丁
打补丁的临时方式修改，并不会修改原文件假如修改replicas个数
[root@linuxea linuxea]# kubectl patch deployment dpment-linuxea -p '{"spec":{"replicas":5}}'
deployment.extensions/dpment-linuxea patched其中， kubectl patch 后跟name，使用-p花括号的方式，大致这样：'{"spec":{"replicas":5}}'，修改完成使用kubectl get rs查看
[root@linuxea linuxea]# kubectl get rs
NAME DESIRED CURRENT READY AGE
dpment-linuxea-648d599b5f 5 5 5 1d
dpment-linuxea-65b8d94cc6 0 0 0 1d
linuxea.com 5 5 5 2d
nginx-linuxea-5786698598 3 3 3 6d查看pods，已经打补丁修改完成
[root@linuxea linuxea]# kubectl get pods
NAME READY STATUS RESTARTS AGE
client-linuxea 1/1 Running 0 9d
dpment-linuxea-648d599b5f-8shps 1/1 Running 0 26s
dpment-linuxea-648d599b5f-94pd2 1/1 Running 0 1d
dpment-linuxea-648d599b5f-blrzr 1/1 Running 0 1d
dpment-linuxea-648d599b5f-ccj9c 1/1 Running 0 26spatch2
当前五个pod,最多不可用0个，最大在线可用数量为6个，并且更新第一个就暂停下来
- 修改策略
打补丁进行修改上述策略
[root@linuxea linuxea]# kubectl patch deployment dpment-linuxea -p '{"spec":{"strategy":{"rollingUpdate":{"maxSurge":1,"maxUnavailable":0}}}}'
deployment.extensions/dpment-linuxea patched[root@linuxea linuxea]# kubectl describe deployment dpment-linuxea|grep RollingUpdateStrategy
RollingUpdateStrategy: 0 max unavailable, 1 max surge上述RollingUpdateStrategy: 0 max unavailable, 1 max surge已经从25%修改
- 更新
set image
set image deployment dpment-linuxea，其中nginx-a是yaml文件中name值，而后使用pause 停止kubectl rollout pause deployment dpment-linuxea使用set image 修改成nginx:1.14.c（这个镜像内容和nginx:1.14.b一样）
- pause: 暂停更新
- resume: 继续此前的更新
[root@linuxea linuxea]# kubectl set image deployment dpment-linuxea nginx-a=marksugar/nginx:1.14.c &&kubectl rollout pause deployment dpment-linuxea
deployment.extensions/dpment-linuxea image updated
deployment.extensions/dpment-linuxea paused更新完成第一个就会停止,kubectl get pods -l version=v0.1.32 --show-labels -w监视,或者不看标签
[root@linuxea linuxea]# kubectl get pods -l version=v0.1.32 -w
NAME READY STATUS RESTARTS AGE
dpment-linuxea-65b8d94cc6-dlmjw 1/1 Running 0 3m
dpment-linuxea-65b8d94cc6-fxg9h 1/1 Running 0 3m
dpment-linuxea-65b8d94cc6-nlnjd 1/1 Running 0 3m
dpment-linuxea-65b8d94cc6-w4grl 1/1 Running 0 11m
dpment-linuxea-65b8d94cc6-x79t2 1/1 Running 0 3m
dpment-linuxea-745fd95894-ln886 0/1 Pending 0 0s
dpment-linuxea-745fd95894-ln886 0/1 Pending 0 0s
dpment-linuxea-745fd95894-ln886 0/1 ContainerCreating 0 0s
dpment-linuxea-745fd95894-ln886 1/1 Running 0 5s或者使用 kubectl rollout status deployment dpment-linuxea查看
[root@linuxea ~]# kubectl rollout status deployment dpment-linuxea
Waiting for deployment "dpment-linuxea" rollout to finish: 1 out of 5 new replicas have been updated...- rollout
但被更新的这台是想要的结果，而后在更新其他
[root@linuxea ~]# kubectl rollout resume deployment dpment-linuxea
deployment.extensions/dpment-linuxea resumed在观察 kubectl rollout status deployment dpment-linuxea结果
[root@linuxea ~]# kubectl rollout status deployment dpment-linuxea
Waiting for deployment "dpment-linuxea" rollout to finish: 1 out of 5 new replicas have been updated...
Waiting for deployment spec update to be observed...
Waiting for deployment spec update to be observed...
Waiting for deployment "dpment-linuxea" rollout to finish: 1 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 1 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 2 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 2 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 3 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 3 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 3 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 3 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 4 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 4 out of 5 new replicas have been updated...
Waiting for deployment "dpment-linuxea" rollout to finish: 2 old replicas are pending termination...
Waiting for deployment "dpment-linuxea" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "dpment-linuxea" rollout to finish: 1 old replicas are pending termination...
deployment "dpment-linuxea" successfully rolled out在观察更新过程
[root@linuxea linuxea]# kubectl get pods -l version=v0.1.32 -w
NAME READY STATUS RESTARTS AGE
dpment-linuxea-65b8d94cc6-dlmjw 1/1 Running 0 3m
dpment-linuxea-65b8d94cc6-fxg9h 1/1 Running 0 3m
dpment-linuxea-65b8d94cc6-nlnjd 1/1 Running 0 3m
dpment-linuxea-65b8d94cc6-w4grl 1/1 Running 0 11m
dpment-linuxea-65b8d94cc6-x79t2 1/1 Running 0 3m
dpment-linuxea-745fd95894-ln886 0/1 Pending 0 0s
dpment-linuxea-745fd95894-ln886 0/1 Pending 0 0s
dpment-linuxea-745fd95894-ln886 0/1 ContainerCreating 0 0s
dpment-linuxea-745fd95894-ln886 1/1 Running 0 5s
dpment-linuxea-65b8d94cc6-dlmjw 1/1 Terminating 0 5m
dpment-linuxea-745fd95894-f58tj 0/1 Pending 0 0s
dpment-linuxea-745fd95894-f58tj 0/1 Pending 0 0s
dpment-linuxea-745fd95894-f58tj 0/1 ContainerCreating 0 0s
dpment-linuxea-745fd95894-f58tj 1/1 Running 0 5s
dpment-linuxea-65b8d94cc6-nlnjd 1/1 Terminating 0 5m
dpment-linuxea-745fd95894-4c2nr 0/1 Pending 0 0s
dpment-linuxea-745fd95894-4c2nr 0/1 Pending 0 0s
dpment-linuxea-745fd95894-4c2nr 0/1 ContainerCreating 0 0s
dpment-linuxea-745fd95894-4c2nr 1/1 Running 0 4s
dpment-linuxea-65b8d94cc6-fxg9h 1/1 Terminating 0 6m
dpment-linuxea-745fd95894-2xwcp 0/1 Pending 0 0s
dpment-linuxea-745fd95894-2xwcp 0/1 Pending 0 0s
dpment-linuxea-745fd95894-2xwcp 0/1 ContainerCreating 0 0s
dpment-linuxea-745fd95894-2xwcp 1/1 Running 0 1s
dpment-linuxea-65b8d94cc6-x79t2 1/1 Terminating 0 6m
dpment-linuxea-745fd95894-5rpdc 0/1 Pending 0 0s
dpment-linuxea-745fd95894-5rpdc 0/1 Pending 0 0s
dpment-linuxea-745fd95894-5rpdc 0/1 ContainerCreating 0 0s
dpment-linuxea-745fd95894-5rpdc 1/1 Running 0 1ss在查看rs，此刻历史版本有marksugar/nginx:1.14.a,marksugar/nginx:1.14.b,marksugar/nginx:1.14.c三个镜像
[root@linuxea linuxea]# kubectl get rs -o wide -l app=linuxea_app
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
dpment-linuxea-648d599b5f 0 0 0 1d nginx-a marksugar/nginx:1.14.b app=linuxea_app,pod-template-hash=2048155619,version=v0.1.32
dpment-linuxea-65b8d94cc6 0 0 0 1d nginx-a marksugar/nginx:1.14.a app=linuxea_app,pod-template-hash=2164850772,version=v0.1.32
dpment-linuxea-745fd95894 5 5 5 3m nginx-a marksugar/nginx:1.14.c app=linuxea_app,pod-template-hash=3019851450,version=v0.1.32- 回滚
此刻，发现c镜像有问题，即可进行回滚，undo（如果不指定，默认回滚上一个）首先，需要知道当前版本号REVISION,使用kubectl rollout history deployment dpment-linuxea 获取
[root@linuxea linuxea]# kubectl rollout history deployment dpment-linuxea
deployments "dpment-linuxea"
REVISION CHANGE-CAUSE
2 <none>
3 <none>
4 <none>而后进行回滚。--to-revision制定版本号REVISION
[root@linuxea linuxea]# kubectl rollout undo deployment dpment-linuxea --to-revision=2
deployment.extensions/dpment-linuxea按照之前的rs顺序，结合rollout history,指定版本2的镜像应该是marksugar/nginx:1.14.b(此前回滚一次，1被滚动成4)
[root@linuxea linuxea]# kubectl get rs -o wide
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
dpment-linuxea-648d599b5f 5 5 5 1d nginx-a marksugar/nginx:1.14.b app=linuxea_app,pod-template-hash=2048155619,version=v0.1.32
dpment-linuxea-65b8d94cc6 0 0 0 1d nginx-a marksugar/nginx:1.14.a app=linuxea_app,pod-template-hash=2164850772,version=v0.1.32
dpment-linuxea-745fd95894 0 0 0 12m nginx-a marksugar/nginx:1.14.c app=linuxea_app,pod-template-hash=3019851450,version=v0.1.32在看历史版本
[root@linuxea linuxea]# kubectl rollout history deployment dpment-linuxea
deployments "dpment-linuxea"
REVISION CHANGE-CAUSE
3 <none>
4 <none>
5 <none>其中第二版已经被滚动到REVISION5
