kubernetes Service 详解

2024-01-09 07:27:41

写在前面：如有问题，以你为准，

目前24年应届生，各位大佬轻喷，部分资料与图片来自网络

内容较长，页面右上角目录方便跳转

Service 介绍架构

在kubernetes中，Pod是应用程序的载体，我们可以通过Pod的IP来访问应用程序，但是Pod的IP地址不是固定的，这就意味着不方便直接采用Pod的IP对服务进行访问。
1. Pod IP 会随着Pod的重建产生变化
2. Pod IP 仅仅是集群内可见的虚拟IP,外部无法访问
为了解决这个问题，kubernetes提供了Service资源，Service会对提供同一个服务的多个Pod进行聚合，并且提供一个统一的入口地址，通过访问Service的入口地址就能访问到后面的Pod服务。
架构如图

注：通过labels标签选择器来将service与后端Pod进行绑定

Service在很多情况下只是一个概念，真正起作用的其实是kube-proxy服务进程，每个Node节点上都运行了一个kube-proxy的服务进程。当创建Service的时候会通过API Server向etcd写入创建的Service的信息，而kube-proxy会基于监听的机制发现这种Service的变化，然后它会将最新的Service信息转换为对应的。
访问规则即流量负载分发 使用ipvs实现，其也是实现LVS的核心

# 10.97.97.97:80 是service提供的访问入口（VIP）

# 当访问这个入口的时候，可以发现后面有三个pod的服务在等待调用，

# kube-proxy会基于rr（轮询）的策略，将请求分发到其中一个pod上去

# 这个规则会同时在集群内的所有节点上都生成，所以在任何一个节点上访问都可以。

[root@k8s-node1 ~]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

?-> RemoteAddress:Port? Forward Weight ActiveConn InActConn

?TCP 10.97.97.97:80 rr

??-> 10.244.1.39:80 ? Masq? 1? 0? 0

??-> 10.244.1.40:80 ? Masq? 1? 0 ?0

??-> 10.244.2.33:80?? Masq? 1? 0? 0

kube-proxy（service 工作原理）

kube-proxy目前支持三种工作模式：

是逐步进化的，从userspace 到 iptables 再到 ipvs

1. userspace 模式：
  1. userspace模式下，kube-proxy会为每一个Service创建一个监听端口，发向Cluster IP的请求被iptables规则重定向到kube-proxy监听的端口上，kube-proxy根据LB算法（负载均衡算法）选择一个提供服务的Pod并和其建立连接，以便将请求转发到Pod上。
  2. 该模式下，kube-proxy充当了一个四层负载均衡器的角色。由于kube-proxy运行在userspace中，在进行转发处理的时候会增加内核和用户空间之间的数据拷贝，虽然比较稳定，但是效率非常低下。
1. iptables 模式：
  1. iptables模式下，kube-proxy为Service后端的每个Pod创建对应的iptables规则，直接将发向Cluster IP的请求重定向到一个Pod的IP上。
  2. 该模式下kube-proxy不承担四层负载均衡器的角色，只负责创建iptables规则。该模式的优点在于较userspace模式效率更高，但是不能提供灵活的LB策略，当后端Pod不可用的时候无法进行重试。
1. ipvs?模式：
  1. ipvs模式和iptables类似，kube-proxy监控Pod的变化并创建相应的ipvs规则。ipvs相对iptables转发效率更高，除此之外，ipvs支持更多的LB算法。
开启ipvs（必须安装ipvs内核模块，否则会降级为iptables）

ipvs

开启查看 ipvs

# 更改模式 vim 下输入/mode

[root@master ~]# kubectl edit cm kube-proxy -n kube-system

??? kind: KubeProxyConfiguration

??? metricsBindAddress: ""

??? mode: "ipvs"

??? nodePortAddresses: null

# 查看与重新创建每个node 对应的 kube-proxy（三个node）??????

[root@master ~]# kubectl get pod -l k8s-app=kube-proxy -n kube-system

NAME?????????????? READY?? STATUS??? RESTARTS????? AGE

kube-proxy-b8mzd?? 1/1???? Running?? 0???????????? 13d

kube-proxy-g6q8z?? 1/1???? Running?? 4 (23h ago)?? 13d

kube-proxy-trzb9?? 1/1???? Running?? 3 (23h ago)?? 12d

[root@master ~]# kubectl delete pod -l k8s-app=kube-proxy -n kube-system

pod "kube-proxy-b8mzd" deleted

pod "kube-proxy-g6q8z" deleted

pod "kube-proxy-trzb9" deleted

[root@master ~]# kubectl get pod -l k8s-app=kube-proxy -n kube-system

NAME?????????????? READY?? STATUS??? RESTARTS?? AGE

kube-proxy-cppq6?? 1/1???? Running?? 0????????? 8s

kube-proxy-cw8xn?? 1/1???? Running?? 0????????? 9s

kube-proxy-nlnpl?? 1/1???? Running?? 0????????? 9s

查看 ipvs 配置

[root@master ~]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

? -> RemoteAddress:Port?????????? Forward Weight ActiveConn InActConn

TCP? 10.96.0.1:443 rr

? -> 192.168.100.53:6443????????? Masq??? 1????? 1????????? 0????????

TCP? 10.96.0.10:53 rr

? -> 10.244.219.65:53???????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.219.69:53???????????? Masq??? 1????? 0????????? 0????????

TCP? 10.96.0.10:9153 rr

? -> 10.244.219.65:9153?????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.219.69:9153?????????? Masq??? 1????? 0????????? 0????????

TCP? 10.98.145.184:9094 rr

? -> 10.244.219.67:9094?????????? Masq??? 1????? 0????????? 0????????

TCP? 10.98.165.172:443 rr

? -> 192.168.100.51:4443????????? Masq??? 1????? 0????????? 0????????

? -> 192.168.100.52:4443????????? Masq??? 1????? 0????????? 0????????

TCP? 10.109.241.243:5473 rr

? -> 192.168.100.51:5473????????? Masq??? 1????? 0????????? 0????????

? -> 192.168.100.52:5473????????? Masq??? 1????? 0????????? 0????????

TCP? 10.111.111.114:443 rr

? -> 10.244.219.66:5443?????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.219.68:5443?????????? Masq??? 1????? 0????????? 0????????

UDP? 10.96.0.10:53 rr

? -> 10.244.219.65:53???????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.219.69:53???????????? Masq??? 1????? 0????????? 0???????

负载分发策略

对Service的访问被分发到了后端的Pod上去，目前kubernetes提供了两种负载分发策略：
1. 如果不定义，默认使用kube-proxy的策略，比如随机、轮询等。
2. 基于客户端地址的会话保持模式，即来自同一个客户端发起的所有请求都会转发到固定的一个Pod上，这对于传统基于Session的认证项目来说很友好，此模式可以在spec中添加sessionAffinity: ClientIP选项。
查看ipvs的映射规则，rr表示轮询：

[root@master k8s]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

? -> RemoteAddress:Port?????????? Forward Weight ActiveConn InActConn

???

TCP? 10.97.97.97:80 rr # vip:端口 rr（轮询策略）

? -> 10.244.104.10:80???????????? Masq??? 1????? 0????????? 1????????

? -> 10.244.166.129:80??????????? Masq??? 1????? 0????????? 1????????

? -> 10.244.166.191:80??????????? Masq??? 1????? 0????????? 2?

[root@master k8s]# curl 10.97.97.97

?IP: 10.244.166.191 pod-1 node1

[root@master k8s]# curl 10.97.97.97

?IP: 10.244.166.129 pod-2 node1

[root@master k8s]# curl 10.97.97.97

?IP: 10.244.104.10 pod-3 node2

Endpoint

Endpoint是kubernetes中的一个资源对象，存储在etcd中，用来记录一个service对应的所有Pod的访问地址，它是根据service配置文件中的selector描述产生的。
一个service由一组Pod组成，这些Pod通过Endpoints暴露出来，Endpoints是实现实际服务的端点集合。换言之，service和Pod之间的联系是通过Endpoints实现的，也就是通过labels 进行 selector 实现service 与Pod之间的绑定

[root@master k8s]# kubectl describe service -n study service-clusterip

Name:????????????? service-clusterip

Namespace:???????? study

Labels:??????????? <none>

Annotations:?????? <none>

Selector:????????? app=nginx-pod

Type:????????????? ClusterIP

IP Family Policy:? SingleStack

IP Families:?????? IPv4

IP:??????????????? 10.97.97.97

IPs:?????????????? 10.97.97.97

Port:????????????? <unset>? 80/TCP

TargetPort:??????? 80/TCP

Endpoints:???????? 10.244.1.39:80,10.244.1.40:80 #连接的pod

Session Affinity:? None

Events:??????????? <none>

[root@master k8s]# kubectl get endpoints -n study -o wide

NAME??????????????? ENDPOINTS??????????????????????? AGE

service-clusterip?? 10.244.1.39:80,10.244.1.40:80?? 5m47s

域名

当我们创建一个 Service 的时候，Kubernetes 会创建一个相应的 DNS 条目。
该条目的形式是

<service-name>.

<namespace-name>.svc.cluster.local，这意味着如果容器中只使用

<服务名称>，它将被解析到本地名称空间的服务器。这对于跨多个名字空间（如开发、测试和生产）使用相同的配置非常有用。如果你希望跨名字空间访问，则需要使用完全限定域名（FQDN）

自带 service

[root@master cks]# kubectl get svc

NAME???????? TYPE??????? CLUSTER-IP?? EXTERNAL-IP?? PORT(S)?? AGE

kubernetes?? ClusterIP?? 10.96.0.1??? <none>??????? 443/TCP?? 278d

kubernetes 用于给 pod 访问 kube apiserver

Service 类型（实操）

命令行实操（expose）

集群内部访问

# 创建 deploy

[root@master k8s]# kubectl create deployment nginx -n default? --image=nginx:1.8 --replicas=2

deployment.apps/nginx created

# 暴露端口，其实就是创建 service

[root@master k8s]# kubectl expose deploy nginx --name=nginx --type=ClusterIP --port=80 --target-port=80 -n default

service/nginx exposed

[root@master k8s]# kubectl get svc -n default

NAME???????? TYPE??????? CLUSTER-IP????? EXTERNAL-IP?? PORT(S)?? AGE

kubernetes?? ClusterIP?? 10.96.0.1?????? <none>??????? 443/TCP?? 2d

nginx??????? ClusterIP?? 10.105.198.94?? <none>??????? 80/TCP??? 22s

[root@master k8s]# curl 10.105.198.94 #集群内部地址

[root@master k8s]# kubectl delete? svc nginx -n default

service "nginx" deleted

集群外部访问

[root@master k8s]# kubectl expose deploy nginx --name=nginx --type=NodePort --port=80 --target-port=80 -n default

service/nginx exposed

[root@master k8s]# kubectl get svc -n default

NAME???????? TYPE??????? CLUSTER-IP????? EXTERNAL-IP?? PORT(S)??????? AGE

kubernetes?? ClusterIP?? 10.96.0.1?????? <none>??????? 443/TCP??????? 2d

nginx??????? NodePort??? 10.105.143.21?? <none>??????? 80:31627/TCP?? 7s

#? 80:31627/TCP 中 31627 是master的ip地址端口，

# 会将master ip:31627 请求转发到 10.105.143.21

[root@master k8s]# curl 192.168.100.53:31627

[root@master k8s]# kubectl delete? svc nginx -n default

service "nginx" deleted

yaml 整体解析

spec.type：

? ClusterIP：默认值，它是kubernetes系统自动分配的虚拟IP，只能在集群内部访问。

? NodePort：将Service通过指定的Node（集群节点上）上的端口暴露给外部，通过此方法，就可以在集群外部访问服务。

? LoadBalancer：使用外接负载均衡器完成到服务的负载分发，注意此模式需要外部云环境的支持。

? ExternalName：把集群外部的服务引入集群内部，直接使用，可以实现pod访问外部域名地址

sessionAffinity：ClientIP 同一个ip都全部请求去同一个Pod上（会话保持模式）

NodePort???? 的缺点是会占用很多集群机器的端口，那么当集群服务变多的时候，这个缺点就愈发明显。

LoadBalancer 的缺点是每个Service都需要一个LB，浪费，麻烦，并且需要kubernetes之外的设备的支持

Ingress 只需要一个NodePort或者一个LB就可以满足暴露多个Service的需

apiVersion: v1 # 版本

kind: Service # 类型

metadata: # 元数据

? name: # 资源名称

? namespace: # 命名空间

spec:

? selector: # 标签选择器，用于确定当前Service代理那些Pod

??? app: nginx

? type: NodePort # Service的类型，指定Service的访问方式

? clusterIP: # 虚拟服务的IP地址

? sessionAffinity: # session亲和性，支持ClientIP、None两个选项，默认值为None（不开启）

? ports: # 端口信息

??? - port: 8080 # Service 开放端口

????? protocol: TCP # 协议

????? targetPort : # 转发到 Pod 的端口

????? nodePort:? # 主机 开放端口

环境准备

创建deployment控制器，注意labels为 app=nginx-pod

---

apiVersion: apps/v1

kind: Namespace

metadata:

? name: study

---

apiVersion: apps/v1

kind: Deployment

metadata:

? name: service-environment-deployment

? namespace: study

spec:

? replicas: 3

? selector:

??? matchLabels:

????? app: nginx-pod

? template:

??? metadata:

????? labels:

??????? app: nginx-pod

??? spec:

????? containers:

??????? - name: nginx

????????? image: nginx:1.17.1

????????? ports:

??????????? - containerPort: 80 # 容器开放端口

[root@master k8s]# kubectl apply -f controller.yaml

namespace/study created

deployment.apps/service-environment-deployment created



[root@master k8s]# kubectl get deploy -n study

NAME???????????????????????????? READY?? UP-TO-DATE?? AVAILABLE?? AGE

service-environment-deployment?? 3/3???? 3??????????? 3?????????? 21s

[root@master k8s]# kubectl get pod -n study -o wide --show-labels

NAME???????????????????????????????????? ?????????READY?? STATUS??? RESTARTS?? AGE?? IP?????????????? NODE??? NOMINATED NODE?? READINESS GATES?? LABELS

service-environment-deployment-6bb9d9f778-5k2x6?? 1/1???? Running?? 0????????? 57s?? 10.244.166.191?? node1?? <none>?????????? <none>??????????? app=nginx-pod,pod-template-hash=6bb9d9f778

service-environment-deployment-6bb9d9f778-8bt7j?? 1/1???? Running?? 0????????? 57s?? 10.244.166.129?? node1?? <none>?????????? <none>??????????? app=nginx-pod,pod-template-hash=6bb9d9f778

service-environment-deployment-6bb9d9f778-8hcm2?? 1/1???? Running?? 0????????? 57s?? 10.244.104.10??? node2?? <none>?????????? <none>??????????? app=nginx-pod,pod-template-hash=6bb9d9f778

进入pod里面修改index

[root@master k8s]# kubectl exec -it -n study service-environment-deployment-6bb9d9f778-5k2x6 -c nginx /bin/sh

echo " IP: 10.244.166.191 pod-1 node1" > /usr/share/nginx/html/index.html



[root@master k8s]# kubectl exec -it -n study service-environment-deployment-6bb9d9f778-8bt7j -c nginx /bin/sh

echo " IP: 10.244.166.129 pod-2 node1" > /usr/share/nginx/html/index.html
[root@master k8s]# kubectl exec -it -n study service-environment-deployment-6bb9d9f778-8hcm2 -c nginx /bin/sh

echo " IP: 10.244.104.10 pod-3 node2" > /usr/share/nginx/html/index.html

[root@master k8s]# curl 10.244.166.191

?IP: 10.244.166.191 pod-1 node1

[root@master k8s]# curl 10.244.166.129

?IP: 10.244.166.129 pod-2 node1

[root@master k8s]# curl 10.244.104.10

?IP: 10.244.104.10 pod-3 node2

?ClusterIP 类型

只能在集群内部访问

yaml 编写

apiVersion: v1

kind: Service

metadata:

? name: service-clusterip

? namespace: study

spec:

? selector:

??? app: nginx-pod # Pod的标签

? clusterIP: 10.97.97.97 # service的IP地址，如果不写，默认会生成一个

? type: ClusterIP

? ports:

??? - port: 80 # Service的端口

????? protocol: TCP # 协议

????? targetPort: 80 # Pod的端口

创建查看检测

[root@master k8s]# kubectl apply -f service.yaml

service/service-clusterip created

[root@master k8s]# kubectl get service -n study

NAME??????????????? TYPE??????? CLUSTER-IP??? EXTERNAL-IP?? PORT(S)?? AGE

service-clusterip?? ClusterIP?? 10.97.97.97?? <none>??????? 80/TCP??? 10s

[root@master k8s]# kubectl describe service -n study service-clusterip

Name:????????????? service-clusterip

Namespace:???????? study

Labels:??????????? <none>

Annotations:?????? <none>

Selector:????????? app=nginx-pod

Type:????????????? ClusterIP

IP Family Policy:? SingleStack

IP Families:?????? IPv4

IP:??????????????? 10.97.97.97

IPs:?????????????? 10.97.97.97

Port:????????????? <unset>? 80/TCP

TargetPort:??????? 80/TCP

Endpoints:???????? 10.244.104.10:80,10.244.166.129:80,10.244.166.191:80 #连接的pod

Session Affinity:? None

Events:??????????? <none>

[root@master k8s]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

? -> RemoteAddress:Port?????????? Forward Weight ActiveConn InActConn
TCP? 10.97.97.97:80 rr #vip:端口 rr（轮询策略）

? -> 10.244.104.10:80???????????? Masq??? 1????? 0????????? 1????????

? -> 10.244.166.129:80??????????? Masq??? 1????? 0????????? 1????????

? -> 10.244.166.191:80??????????? Masq??? 1????? 0????????? 2?

# 由下面可以看到是轮询策略

[root@master k8s]# curl 10.97.97.97

?IP: 10.244.166.191 pod-1 node1

[root@master k8s]# curl 10.97.97.97

?IP: 10.244.166.129 pod-2 node1

[root@master k8s]# curl 10.97.97.97

?IP: 10.244.104.10 pod-3 node2

删除

[root@master k8s]# kubectl delete -f service.yaml

service "service-clusterip" deleted

HeadLiness 类型

在某些场景中，开发人员可能不想使用Service提供的负载均衡功能，而希望自己来控制负载均衡策略，针对这种情况，kubernetes提供了HeadLinesss Service，这类Service不会分配Cluster IP，如果想要访问Service，只能通过Service的域名进行访问

一般用于实现 StatefulSet（常用来部署RabbitMQ集群、Zookeeper集群、MySQL集群、Eureka集群等）

apiVersion: v1

kind: Service

metadata:

? name: service-headliness

? namespace: study

spec:

? selector:

??? app: nginx-pod

? clusterIP: None # 将clusterIP设置为None，即可创建headliness Service

? type: ClusterIP

? ports:

??? - port: 80 # Service的端口

????? targetPort: 80 # Pod的端口

创建查看

[root@master k8s]# kubectl apply -f service.yaml

service/service-headliness created

[root@master k8s]# kubectl get svc -n study

NAME???????????????? TYPE??????? CLUSTER-IP?? EXTERNAL-IP?? PORT(S)?? AGE

service-headliness?? ClusterIP?? None???????? <none>??????? 80/TCP??? 8s

[root@master k8s]# kubectl describe svc service-headliness -n study

Name:????????????? service-headliness

Namespace:???????? study

Labels:??????????? <none>

Annotations:?????? <none>

Selector:????????? app=nginx-pod

Type:????????????? ClusterIP

IP Family Policy:? SingleStack

IP Families:?????? IPv4

IP:??????????????? None

IPs:?????????????? None

Port:????????????? <unset>? 80/TCP

TargetPort:??????? 80/TCP

Endpoints:???????? 10.244.104.10:80,10.244.166.129:80,10.244.166.191:80

Session Affinity:? None

Events:??????????? <none>

查看域名解析情况

[root@master k8s]# kubectl get pod -n study

NAME????????????????????????????????????????????? READY?? STATUS??? RESTARTS?? AGE

service-environment-deployment-6bb9d9f778-5k2x6?? 1/1???? Running?? 0????????? 45m

service-environment-deployment-6bb9d9f778-8bt7j?? 1/1???? Running?? 0????????? 45m

service-environment-deployment-6bb9d9f778-8hcm2?? 1/1???? Running?? 0????????? 45m

[root@master k8s]# kubectl exec -it -n study service-environment-deployment-6bb9d9f778-5k2x6 -c nginx /bin/sh

kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.

# cat /etc/resolv.conf

nameserver 10.96.0.10

search study.svc.cluster.local svc.cluster.local cluster.local

options ndots:5

进行域名查询

[root@master k8s]# dig @10.96.0.10 service-headliness.study.svc.cluster.local

; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el8 <<>> @10.96.0.10 service-clusterip.study.svc.cluster.local

; (1 server found)

;; global options: +cmd

;; Got answer:

;; WARNING: .local is reserved for Multicast DNS

;; You are currently testing what happens when an mDNS query is leaked to DNS

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6641

;; flags: qr aa rd; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

;; WARNING: recursion requested but not available
;; OPT PSEUDOSECTION:

; EDNS: version: 0, flags:; udp: 4096

; COOKIE: 2ea4525b90a0ac1b (echoed)

;; QUESTION SECTION:

;service-headliness.study.svc.cluster.local. IN A


;; ANSWER SECTION:

service-headliness.study.svc.cluster.local. 30 IN A 10.244.104.10

service-headliness.study.svc.cluster.local. 30 IN A 10.244.166.191

service-headliness.study.svc.cluster.local. 30 IN A 10.244.166.129


;; Query time: 18 msec

;; SERVER: 10.96.0.10#53(10.96.0.10)

;; WHEN: Wed Feb 15 09:43:58 EST 2023

;; MSG SIZE? rcvd: 253

NodePort 类型

NodePort的工作原理就是将Service的端口映射到Node的一个端口上，然后就可以通过

NodeIP:NodePort 来访问Service了

可以在集群外部访问服务

yaml 编写

apiVersion: v1

kind: Service

metadata:

? name: service-nodeport

? namespace: study

spec:

? selector:

??? app: nginx-pod

? type: NodePort # Service类型为NodePort,实现集群外部访问

? ports:

??? - port: 80 # Service的端口

????? targetPort: 80 # Pod的端口

????? nodePort: 30002

????? # 指定绑定的node的端口（默认取值范围是30000~32767），如果不指定，会默认分配

[root@master k8s]# kubectl apply -f service.yaml

service/service-nodeport created

[root@master k8s]# kubectl get svc -n study

NAME?????????????? TYPE?????? CLUSTER-IP???? EXTERNAL-IP?? PORT(S)??????? AGE

service-nodeport?? NodePort?? 10.100.46.87?? <none>??????? 80:30002/TCP?? 48s

[root@master k8s]# ifconfig | grep inet

??????? inet6 fe80::ecee:eeff:feee:eeee? prefixlen 64? scopeid 0x20<link>

??????? inet6 fe80::ecee:eeff:feee:eeee? prefixlen 64? scopeid 0x20<link>

??????? inet6 fe80::ecee:eeff:feee:eeee? prefixlen 64? scopeid 0x20<link>

??????? inet6 fe80::ecee:eeff:feee:eeee? prefixlen 64? scopeid 0x20<link>

??????? inet6 fe80::ecee:eeff:feee:eeee? prefixlen 64? scopeid 0x20<link>

??????? inet 192.168.100.53? netmask 255.255.255.0? broadcast 192.168.100.255

??????? inet6 fe80::5523:b3a4:8bc9:b40f? prefixlen 64? scopeid 0x20<link>

??????? inet6 fe80::522c:e0a0:2c74:37c6? prefixlen 64? scopeid 0x20<link>

??????? inet6 fe80::dec0:9c00:3416:2561? prefixlen 64? scopeid 0x20<link>

??????? inet 127.0.0.1? netmask 255.0.0.0

??????? inet6 ::1? prefixlen 128? scopeid 0x10<host>

[root@master k8s]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

? -> RemoteAddress:Port?????????? Forward Weight ActiveConn InActConn

TCP? 192.168.100.53:30002 rr

? -> 10.244.104.10:80???????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.166.129:80??????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.166.191:80??????????? Masq??? 1????? 0????????? 0???

# 另开一台同一网络的linux或windows进行访问，地址为 masterip 192.168.100.53

[root@ip-15 ~]# curl 192.168.100.53:30002

?IP: 10.244.166.191 pod-1 node1

[root@ip-15 ~]# curl 192.168.100.53:30002

?IP: 10.244.166.129 pod-2 node1

[root@ip-15 ~]# curl 192.168.100.53:30002

?IP: 10.244.104.10 pod-3 node2

扩展，访问集群中你的节点也是可以的如 node1 node2

[root@node1 ~]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

? -> RemoteAddress:Port?????????? Forward Weight ActiveConn InActConn

TCP? 192.168.100.51:30002 rr

? -> 10.244.104.10:80???????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.166.129:80??????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.166.191:80??????????? Masq??? 1????? 0????????? 0?

[root@ip-15 ~]# curl 192.168.100.51:30002

?IP: 10.244.166.191 pod-1 node1

[root@ip-15 ~]# curl 192.168.100.51:30002

?IP: 10.244.166.129 pod-2 node1

[root@ip-15 ~]# curl 192.168.100.51:30002

?IP: 10.244.104.10 pod-3 node2

LoadBalancer 类型

LoadBalancer和NodePort很相似，目的都是向外部暴露一个端口，区别在于LoadBalancer会在集群的外部再来做一个负载均衡设备，而这个设备需要外部环境的支持，外部服务发送到这个设备上的请求，会被设备负载之后转发到集群中

ExternalName 类型

ExternalName类型的Service用于引入集群外部的服务，它通过externalName属性指定一个服务的地址，然后在集群内部访问此Service就可以访问到外部的服务了，访问外部域名地址

apiVersion: v1

kind: Service

metadata:

? name: service-externalname

? namespace: study

spec:

? type: ExternalName # Service类型为ExternalName

? externalName: www.baidu.com # 改成IP地址也可以

[root@master k8s]# kubectl get svc -n study

NAME?????????????????? TYPE?????????? CLUSTER-IP?? EXTERNAL-IP???? PORT(S)?? AGE

service-externalname?? ExternalName?? <none>?????? www.baidu.com?? <none>??? 55s



[root@master k8s]# dig @10.96.0.10 service-externalname.study.svc.cluster.local



; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el8 <<>> @10.96.0.10 service-externalname.study.svc.cluster.local

; (1 server found)

;; global options: +cmd

;; Got answer:

;; WARNING: .local is reserved for Multicast DNS

;; You are currently testing what happens when an mDNS query is leaked to DNS

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2116

;; flags: qr aa rd; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 1

;; WARNING: recursion requested but not available



;; OPT PSEUDOSECTION:

; EDNS: version: 0, flags:; udp: 4096

; COOKIE: 144210b36fc272dd (echoed)

;; QUESTION SECTION:

;service-externalname.study.svc.cluster.local. IN A



;; ANSWER SECTION:

service-externalname.study.svc.cluster.local. 30 IN CNAME www.baidu.com.

www.baidu.com.30INCNAMEwww.a.shifen.com.

www.a.shifen.com.30INA14.215.177.38

www.a.shifen.com.30INA14.215.177.39



;; Query time: 14 msec

;; SERVER: 10.96.0.10#53(10.96.0.10)

;; WHEN: Wed Feb 15 09:57:33 EST 2023

;; MSG SIZE? rcvd: 263

实现会话保持（持久连接）

其实就是这个参数 sessionAffinity: ClientIP

apiVersion: v1

kind: Service

metadata:

? name: service-clusterip

? namespace: study

spec:

? sessionAffinity: ClientIP # 实现保持会话，如果不开启则填 None

? selector:

??? app: nginx-pod # Pod的标签

? clusterIP: 10.97.97.97 # service的IP地址，如果不写，默认会生成一个

? type: ClusterIP

? ports:

??? - port: 80 # Service的端口

????? protocol: TCP # 协议

????? targetPort: 80 # Pod的端口

[root@master k8s]# kubectl get svc -n study

NAME??????????????? TYPE??????? CLUSTER-IP??? EXTERNAL-IP?? PORT(S)?? AGE

service-clusterip?? ClusterIP?? 10.97.97.97?? <none>??????? 80/TCP??? 14s

[root@master k8s]# kubectl describe svc -n study

Name:????????????? service-clusterip

Namespace:???????? study

Labels:??????????? <none>

Annotations:?????? <none>

Selector:????????? app=nginx-pod

Type:????????????? ClusterIP

IP Family Policy:? SingleStack

IP Families:?????? IPv4

IP:??????????????? 10.97.97.97

IPs:?????????????? 10.97.97.97

Port:????????????? <unset>? 80/TCP

TargetPort:??????? 80/TCP

Endpoints:???????? 10.244.104.10:80,10.244.166.129:80,10.244.166.191:80

Session Affinity:? ClientIP # 设置为这个就是保持会话

Events:??????????? <none>

[root@master k8s]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

? -> RemoteAddress:Port?????????? Forward Weight ActiveConn InActConn

????

TCP? 10.97.97.97:80 rr persistent（保持会话的标志） 10800

（保持会话的时间，单位秒）

? -> 10.244.104.10:80???????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.166.129:80??????????? Masq??? 1????? 0????????? 0????????

? -> 10.244.166.191:80??????????? Masq??? 1????? 0????????? 0???

文章来源:https://blog.csdn.net/weixin_48297181/article/details/135457575
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