控制器
在Kubernetes（简称K8s）中，控制器是负责管理和维护集群中资源状态的组件。控制器监视集群中的对象，并根据它们的预期状态来采取行动，以确保系统的期望状态与实际状态保持一致。
对于自主式pod来说，删除pod之后pod就直接消失了，如果因为一些误操作或pod错误退出，就不会自动恢复，这个时候就需要使用k8s的控制器，使用控制器创建的pod可以进行故障的恢复与自愈，并且也可以做资源调度、配置管理等内容
ReplicaSet控制器
ReplicaSet是Kubernetes中的一种控制器，用于确保一组Pod副本的运行。它定义了所需的Pod副本数量，并监控它们的运行状态，以确保始终有指定数量的副本在运行。
用的不多，大多数环境中使用deployment资源，deployment的功能包括ReplicaSet
定义ReplicaSet时，需要定义要创建的pod的模板，相当于pod做了多份的负载均衡
以下是一个replicatest的示例文件
#查看帮助
kubectl explain rs
apiVersion <string>
kind <string>
metadata <Object>
spec <Object>
status <Object>
kubectl explain rs.spec
minReadySeconds
replicas
selector
template
kubectl explain rs.spec.template.spec #与pod的spec相同
cat > rs.yaml << EOF
apiVersion: apps/v1
kind: ReplicaSet
metadata:
name: rstest
namespace: default
spec:
replicas: 5 #副本数
selector: #筛选器，与pod关联
matchLabels:
user: ws #匹配标签user=ws的pod
template: #pod模板
metadata:
labels: #pod标签
user: ws
spec:
containers:
- name: test1
image: docker.io/library/nginx
imagePullPolicy: IfNotPresent
ports:
- containerPort: 80
startupProbe: #启动探测
periodSeconds: 5
initialDelaySeconds: 10
timeoutSeconds: 5
httpGet:
scheme: HTTP
port: 80
path: /
EOF
kubectl apply -f rs.yaml
kubectl get pods -w | grep Running
rstest-2qbrw 1/1 Running 0 2m34s
rstest-6j9p6 1/1 Running 0 2m34s
rstest-ltpn5 1/1 Running 0 2m34s
rstest-z7h27 1/1 Running 0 2m34s
rstest-z8cnf 1/1 Running 0 2m34s
#desired期望3，current当前启动5，ready就绪5
kubectl get rs
NAME DESIRED CURRENT READY AGE
rstest 5 5 5 2m56s、
#退出其中一个pod，删除或异常退出都可以
kubectl delete pods rstest-hrvtj
#创建了一个新pod
kubectl get pods -w | grep Running
rstest-6j9p6 1/1 Running 0 6m41s
rstest-hrvtj 1/1 Running 0 32s
rstest-ltpn5 1/1 Running 0 6m41s
rstest-z7h27 1/1 Running 0 6m41s
rstest-z8cnf 1/1 Running 0 6m41s
rstest-rmxcq 0/1 Running 0 1s
rstest-rmxcq 0/1 Running 0 10s
rstest-rmxcq 1/1 Running 0 10s
扩容与缩容、更新镜像
#扩容与缩容
#修改yaml文件
...
replicas: 6 #副本数
...
kubectl apply -f rs.yaml
#创建了一个新pod
kubectl get pods -w | grep Running
rstest-6j9p6 1/1 Running 0 12m
rstest-ltpn5 1/1 Running 0 12m
rstest-rmxcq 1/1 Running 0 5m29s
rstest-z7h27 1/1 Running 0 12m
rstest-z8cnf 1/1 Running 0 12m
rstest-zwgnl 0/1 Running 0 1s
rstest-zwgnl 0/1 Running 0 10s
rstest-zwgnl 1/1 Running 0 10s
#修改yaml文件
...
replicas: 2 #副本数
...
kubectl apply -f rs.yaml
#全部被关闭，只剩俩 
文章来源：https://www.toymoban.com/news/detail-812264.html
#手动更新镜像，ReplicaSet无法实现滚动更新
#原本状态
curl 10.10.179.34:80
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="<http://nginx.org/>">nginx.org</a>.<br/>
Commercial support is available at
<a href="<http://nginx.com/>">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
#修改yaml文件
...
image: docker.io/library/tomcat
...
kubectl apply -f rs.yaml
#删除原有pods，因为replicatest无法实现滚动更新，而deployment可以
kubectl delete pods rstest-6j9p6
kubectl delete pods rstest-z8cnf
#因为某些原因没法起来，不过问题不大，注释掉探活部分就起来了
kubectl get pods -w
NAME READY STATUS RESTARTS AGE
rstest-c2m98 1/1 Running 0 3m54s
rstest-xkqnl 1/1 Running 0 3m54s
#当前状态，说明当前镜像已经被修改
curl 10.10.234.124:8080
<!doctype html><html lang="en"><head><title>HTTP Status 404 – Not Found</title><style type="text/css">body {font-family:Tahoma,Arial,sans-serif;} h1, h2, h3, b {color:white;background-color:#525D76;} h1 {font-size:22px;} h2 {font-size:16px;} h3 {font-size:14px;} p {font-size:12px;} a {color:black;} .line {height:1px;background-color:#525D76;border:none;}</style></head><body><h1>HTTP Status 404 – Not Found</h1><hr class="line" /><p><b>Type</b> Status Report</p><p><b>Description</b> The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.</p><hr class="line" /><h3>Apache Tomcat/10.1.17</h3></body></html>[
#清理
kubectl delete -f rs.yaml
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