K8s中RS和Deployment
什么是ReplicaSet？
ReplicaSet是下一代复本控制器。ReplicaSet和 Replication Controller之间的唯一区别是现在的选择器支持。Replication Controller只支持基于等式的selector（env=dev或environment!=qa），但ReplicaSet还支持新的，基于集合的selector（version in (v1.0, v2.0)或env notin (dev, qa)）。在试用时官方推荐ReplicaSet。
大多数kubectl支持Replication Controller的命令也支持ReplicaSets。rolling-update命令有一个例外 。如果您想要滚动更新功能，请考虑使用Deployments。此外， rolling-update命令是必须的，而Deployments是声明式的，因此我们建议通过rollout命令使用Deployments。
虽然ReplicaSets可以独立使用，但是今天它主要被 Deployments 作为协调pod创建，删除和更新的机制。当您使用Deployments时，您不必担心管理他们创建的ReplicaSets。Deployments拥有并管理其ReplicaSets。
何时使用ReplicaSet？
ReplicaSet可确保指定数量的pod“replicas”在任何设定的时间运行。然而，Deployments是一个更高层次的概念，它管理ReplicaSets，并提供对pod的声明性更新以及许多其他的功能。因此，我们建议您使用Deployments而不是直接使用ReplicaSets，除非您需要自定义更新编排或根本不需要更新。
这实际上意味着您可能永远不需要操作ReplicaSet对象：直接使用Deployments并在规范部分定义应用程序。
[root@k8s-master mnt]# cat rs.yaml
apiVersion: apps/v1
kind: ReplicaSet
metadata:
name: frontend
spec:
replicas: 3
selector:
matchLabels:
tier: frontend
template:
metadata:
labels:
tier: frontend
spec:
containers:
- name: myapp
image: wangyanglinux/myapp:v1
env:
- name: GET_HOSTS_FROM
value: dns
ports:
- containerPort: 80
[root@k8s-master mnt]#
[root@k8s-master mnt]# kubectl create -f rs.yaml
replicaset.apps/frontend created
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
frontend-4xs95 1/1 Running 0 12s
frontend-gd5th 1/1 Running 0 12s
frontend-tn9pn 1/1 Running 0 12s
[root@k8s-master mnt]# kubectl delete pod --all
pod "frontend-4xs95" deleted
pod "frontend-gd5th" deleted
pod "frontend-tn9pn" deleted
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
frontend-gh2w5 1/1 Running 0 3m58s
frontend-rd9pl 1/1 Running 0 3m58s
frontend-xg845 1/1 Running 0 3m58s
[root@k8s-master mnt]# kubectl get pod --show-labels
NAME READY STATUS RESTARTS AGE LABELS
frontend-gh2w5 1/1 Running 0 4m38s tier=frontend
frontend-rd9pl 1/1 Running 0 4m38s tier=frontend
frontend-xg845 1/1 Running 0 4m38s tier=frontend
[root@k8s-master mnt]# kubectl get pod --show-labels
NAME READY STATUS RESTARTS AGE LABELS
frontend-btqh8 1/1 Running 0 3s tier=frontend
frontend-gh2w5 1/1 Running 0 7m43s tier=frontend
frontend-rd9pl 1/1 Running 0 7m43s tier=frontend1
frontend-xg845 1/1 Running 0 7m43s tier=frontend
[root@k8s-master mnt]# kubectl delete pod --all
pod "frontend-btqh8" deleted
pod "frontend-gh2w5" deleted
pod "frontend-rd9pl" deleted
pod "frontend-xg845" deleted
[root@k8s-master mnt]# kubectl get pod --show-labels
NAME READY STATUS RESTARTS AGE LABELS
frontend-mnmlm 1/1 Running 0 28s tier=frontend
frontend-x8rcp 1/1 Running 0 27s tier=frontend
frontend-zqs4n 1/1 Running 0 28s tier=frontend
[root@k8s-master mnt]# kubectl delete -f rs.yaml
replicaset.apps "frontend" deleted
[root@k8s-master mnt]# kubectl get pod --show-labels
NAME READY STATUS RESTARTS AGE LABELS
frontend-mnmlm 0/1 Terminating 0 47s tier=frontend
frontend-x8rcp 0/1 Terminating 0 46s tier=frontend
frontend-zqs4n 0/1 Terminating 0 47s tier=frontend
Deployment是什么？
Deployment为Pod和Replica Set（下一代Replication Controller）提供声明式更新。
你只需要在Deployment中描述你想要的目标状态是什么，Deployment controller就会帮你将Pod和Replica Set的实际状态改变到你的目标状态。你可以定义一个全新的Deployment，也可以创建一个新的替换旧的Deployment。
一个典型的用例如下：
- 使用Deployment来创建ReplicaSet。ReplicaSet在后台创建pod。检查启动状态，看它是成功还是失败。
- 然后，通过更新Deployment的PodTemplateSpec字段来声明Pod的新状态。这会创建一个新的ReplicaSet，Deployment会按照控制的速率将pod从旧的ReplicaSet移动到新的ReplicaSet中。
- 如果当前状态不稳定，回滚到之前的Deployment revision。每次回滚都会更新Deployment的revision。
- 扩容Deployment以满足更高的负载。
- 暂停Deployment来应用PodTemplateSpec的多个修复，然后恢复上线。
- 根据Deployment 的状态判断上线是否hang住了。
- 清除旧的不必要的ReplicaSet。
代码展示：
[root@k8s-master mnt]# cat deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
spec:
selector:
matchLabels:
app: nginx
replicas: 3
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: wangyanglinux/myapp:v1
ports:
- containerPort: 80
[root@k8s-master mnt]#
下面的代码包括了扩容和回退和更新。
[root@k8s-master mnt]# kubectl apply -f deployment.yaml --record
deployment.apps/nginx-deployment created
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
nginx-deployment-64ddb75745-fkfxl 0/1 ContainerCreating 0 1s
nginx-deployment-64ddb75745-slcwp 0/1 ContainerCreating 0 1s
nginx-deployment-64ddb75745-vwnqw 0/1 ContainerCreating 0 1s
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
nginx-deployment-64ddb75745-fkfxl 1/1 Running 0 55s
nginx-deployment-64ddb75745-slcwp 1/1 Running 0 55s
nginx-deployment-64ddb75745-vwnqw 1/1 Running 0 55s
[root@k8s-master mnt]# kubectl get rs
NAME DESIRED CURRENT READY AGE
nginx-deployment-64ddb75745 3 3 3 65s
[root@k8s-master mnt]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-deployment-64ddb75745-fkfxl 1/1 Running 0 2m45s 10.244.2.6 k8s-node01 <none> <none>
nginx-deployment-64ddb75745-slcwp 1/1 Running 0 2m45s 10.244.1.9 k8s-node02 <none> <none>
nginx-deployment-64ddb75745-vwnqw 1/1 Running 0 2m45s 10.244.1.8 k8s-node02 <none> <none>
[root@k8s-master mnt]# curl 10.244.2.6
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
[root@k8s-master mnt]# kubectl scale deployment nginx-deployment --replicas 10
deployment.apps/nginx-deployment scaled
[root@k8s-master mnt]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-deployment-64ddb75745-9c55m 0/1 ContainerCreating 0 3s <none> k8s-node01 <none> <none>
nginx-deployment-64ddb75745-9gs9v 0/1 ContainerCreating 0 3s <none> k8s-node01 <none> <none>
nginx-deployment-64ddb75745-fkfxl 1/1 Running 0 4m10s 10.244.2.6 k8s-node01 <none> <none>
nginx-deployment-64ddb75745-nbl92 0/1 ContainerCreating 0 3s <none> k8s-node01 <none> <none>
nginx-deployment-64ddb75745-p4f2z 0/1 ContainerCreating 0 3s <none> k8s-node02 <none> <none>
nginx-deployment-64ddb75745-qtmhl 0/1 ContainerCreating 0 3s <none> k8s-node02 <none> <none>
nginx-deployment-64ddb75745-rgcsl 0/1 ContainerCreating 0 3s <none> k8s-node02 <none> <none>
nginx-deployment-64ddb75745-slcwp 1/1 Running 0 4m10s 10.244.1.9 k8s-node02 <none> <none>
nginx-deployment-64ddb75745-vwnqw 1/1 Running 0 4m10s 10.244.1.8 k8s-node02 <none> <none>
nginx-deployment-64ddb75745-zzmsn 0/1 ContainerCreating 0 3s <none> k8s-node01 <none> <none>
[root@k8s-master mnt]# kubectl describe deployment
Name: nginx-deployment
Namespace: default
CreationTimestamp: Fri, 20 Dec 2019 15:10:03 +0800
Labels: <none>
Annotations: deployment.kubernetes.io/revision: 1
kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{"kubernetes.io/change-cause":"kubectl apply --filename=de ployment.y...
kubernetes.io/change-cause: kubectl apply --filename=deployment.yaml --record=true
Selector: app=nginx
Replicas: 10 desired | 10 updated | 10 total | 10 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 25% max unavailable, 25% max surge
Pod Template:
Labels: app=nginx
Containers:
nginx:
Image: wangyanglinux/myapp:v1
Port: 80/TCP
Host Port: 0/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Progressing True NewReplicaSetAvailable
Available True MinimumReplicasAvailable
OldReplicaSets: <none>
NewReplicaSet: nginx-deployment-64ddb75745 (10/10 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 11m deployment-controller Scaled up replica set nginx-deployment-64ddb75745 to 3
Normal ScalingReplicaSet 7m28s deployment-controller Scaled up replica set nginx-deployment-64ddb75745 to 10
[root@k8s-master mnt]# kubectl rollout history deployment/nginx-deployment
deployment.apps/nginx-deployment
REVISION CHANGE-CAUSE
1 kubectl apply --filename=deployment.yaml --record=true [root@k8s-master mnt]# kubectl set image deployment/nginx-deployment nginx=wangyanglinux/myapp:v2
deployment.apps/nginx-deployment image updated
[root@k8s-master mnt]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-deployment-64ddb75745-rgcsl 0/1 Terminating 0 30m 10.244.1.12 k8s-node02 <none> <none>
nginx-deployment-64ddb75745-slcwp 0/1 Terminating 0 35m 10.244.1.9 k8s-node02 <none> <none>
nginx-deployment-6bd7755b5b-2qwdf 1/1 Running 0 23s 10.244.2.12 k8s-node01 <none> <none>
nginx-deployment-6bd7755b5b-2tpzn 1/1 Running 0 23s 10.244.2.11 k8s-node01 <none> <none>
nginx-deployment-6bd7755b5b-5d2fn 1/1 Running 0 23s 10.244.1.14 k8s-node02 <none> <none>
nginx-deployment-6bd7755b5b-87vdh 1/1 Running 0 23s 10.244.2.13 k8s-node01 <none> <none>
nginx-deployment-6bd7755b5b-fl56p 1/1 Running 0 14s 10.244.1.16 k8s-node02 <none> <none>
nginx-deployment-6bd7755b5b-gpz9q 1/1 Running 0 12s 10.244.1.17 k8s-node02 <none> <none>
nginx-deployment-6bd7755b5b-hhfbn 1/1 Running 0 11s 10.244.2.15 k8s-node01 <none> <none>
nginx-deployment-6bd7755b5b-k5rm7 1/1 Running 0 23s 10.244.1.13 k8s-node02 <none> <none>
nginx-deployment-6bd7755b5b-skh7w 1/1 Running 0 14s 10.244.1.15 k8s-node02 <none> <none>
nginx-deployment-6bd7755b5b-t494q 1/1 Running 0 13s 10.244.2.14 k8s-node01 <none> <none>
[root@k8s-master mnt]# curl 10.244.1.14
Hello MyApp | Version: v2 | <a href="hostname.html">Pod Name</a>
[root@k8s-master mnt]# kubectl get rs
NAME DESIRED CURRENT READY AGE
nginx-deployment-64ddb75745 0 0 0 35m
nginx-deployment-6bd7755b5b 10 10 10 64s
[root@k8s-master mnt]# kubectl rollout undo deployment/nginx-deployment
deployment.apps/nginx-deployment rolled back
[root@k8s-master mnt]# kubectl get pod
NAME READY STATUS RESTARTS AGE
nginx-deployment-64ddb75745-48d5d 1/1 Running 0 11s
nginx-deployment-64ddb75745-4ctzd 1/1 Running 0 13s
nginx-deployment-64ddb75745-8g7f9 1/1 Running 0 13s
nginx-deployment-64ddb75745-bnwlj 1/1 Running 0 9s
nginx-deployment-64ddb75745-gq29d 1/1 Running 0 13s
nginx-deployment-64ddb75745-rp52v 1/1 Running 0 13s
nginx-deployment-64ddb75745-sxch9 1/1 Running 0 10s
nginx-deployment-64ddb75745-tt8tp 0/1 ContainerCreating 0 5s
nginx-deployment-64ddb75745-vtx8w 1/1 Running 0 13s
nginx-deployment-64ddb75745-zr8c7 1/1 Running 0 7s
nginx-deployment-6bd7755b5b-2qwdf 1/1 Terminating 0 3m14s
nginx-deployment-6bd7755b5b-2tpzn 1/1 Terminating 0 3m14s
nginx-deployment-6bd7755b5b-87vdh 1/1 Terminating 0 3m14s
[root@k8s-master mnt]# kubectl get rs
NAME DESIRED CURRENT READY AGE
nginx-deployment-64ddb75745 10 10 10 38m
nginx-deployment-6bd7755b5b 0 0 0 3m29s
[root@k8s-master mnt]# kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-deployment-64ddb75745-48d5d 1/1 Running 0 43s 10.244.2.18 k8s-node01 <none> <none>
nginx-deployment-64ddb75745-4ctzd 1/1 Running 0 45s 10.244.1.18 k8s-node02 <none> <none>
nginx-deployment-64ddb75745-8g7f9 1/1 Running 0 45s 10.244.1.19 k8s-node02 <none> <none>
nginx-deployment-64ddb75745-bnwlj 1/1 Running 0 41s 10.244.1.21 k8s-node02 <none> <none>
nginx-deployment-64ddb75745-gq29d 1/1 Running 0 45s 10.244.2.17 k8s-node01 <none> <none>
nginx-deployment-64ddb75745-rp52v 1/1 Running 0 45s 10.244.1.20 k8s-node02 <none> <none>
nginx-deployment-64ddb75745-sxch9 1/1 Running 0 42s 10.244.2.19 k8s-node01 <none> <none>
nginx-deployment-64ddb75745-tt8tp 1/1 Running 0 37s 10.244.2.20 k8s-node01 <none> <none>
nginx-deployment-64ddb75745-vtx8w 1/1 Running 0 45s 10.244.2.16 k8s-node01 <none> <none>
nginx-deployment-64ddb75745-zr8c7 1/1 Running 0 39s 10.244.1.22 k8s-node02 <none> <none>
[root@k8s-master mnt]# curl 10.244.2.19
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
[root@k8s-master mnt]# kubectl rollout status deployment/nginx-deployment
deployment "nginx-deployment" successfully rolled out
[root@k8s-master mnt]# kubectl rollout history deployment/nginx-deployment
deployment.apps/nginx-deployment
REVISION CHANGE-CAUSE
2 kubectl apply --filename=deployment.yaml --record=true
3 kubectl apply --filename=deployment.yaml --record=true
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