目录
5.2.2、集群外通过NodeIP+nodePort端口访问
一、概述
在k8s中，Pod是应用程序的载体，我们可以通过Pod的IP地址来访问应用程序，但是当Pod宕机后重建后，其IP地址等状态信息可能会变动，也就是说Pod的IP地址不是固定的，这也就意味着不方便直接采用Pod的IP地址对服务进行访问。
为了解决这个问题，k8s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 ，并且将请求负载分发到后端的各个容器应用上 。
Service引入主要是解决Pod的动态变化，提供统一的访问入口：
- 1、防止Pod失联，准备找到提供同一服务的Pod（服务发现）
- 2、定义一组Pod的访问策略（负载均衡）
Service通常是通过Label Selector访问一组Pod，如下图：
其实 Service 只是一个概念，真正起到转发数据的是 kube-proxy 服务进程，kube-proxy 是集群中每个节点上运行的网络代理，每个节点之上都运行一个 kube-proxy 服务进程。当创建 Service 的时候，首先API Server向 etcd 写入 Service 的信息，然后kube-proxy会监听API Server，监听到etcd中 Service 的信息，然后根据Service的信息生成对应的访问规则。
二、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label selector（标签选择器）生成的。
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。
当我们创建Service的时候，如果Service有指定Label Selector（标签选择器）的话，Endpoints控制器会自动创建一个名称跟Service名称一致的Endpoint对象。可简单理解为，Endpoint是一个中间对象，用来存放Service与Pod的映射关系，在Endpoint中，可以看到，当前能正常提供服务的Pod以及不能正常提供的Pod。
例如：
$ kubectl get pod -o wide --show-labels
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES LABELS
nginx-7f456874f4-c7224 1/1 Running 0 20m 192.168.1.3 node01 <none> <none> app=nginx,pod-template-hash=7f456874f4
nginx-7f456874f4-v8pnz 1/1 Running 0 20m 192.168.0.6 controlplane <none> <none> app=nginx,pod-template-hash=7f456874f4
$ kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 14d <none>
nginx ClusterIP 10.109.113.53 <none> 80/TCP 12m app=nginx
$ kubectl get ep
NAME ENDPOINTS AGE
kubernetes 172.30.1.2:6443 14d
nginx 192.168.0.6:80,192.168.1.3:80 12m
# 查看endpoint资源清单
$ kubectl get ep nginx -o yaml
apiVersion: v1
kind: Endpoints
metadata:
annotations:
endpoints.kubernetes.io/last-change-trigger-time: "2023-01-06T06:33:26Z"
creationTimestamp: "2023-01-06T06:33:27Z"
name: nginx # Endpoint名称，跟service的名称一样
namespace: default
resourceVersion: "2212"
uid: 5c1d6639-c27a-4ab5-8832-64c9d618a209
subsets:
- addresses: # Ready addresses表示能正常提供服务的Pod, 还有一个NotReadyAddress表示不能提供正常服务的Pod
- ip: 192.168.0.6 # Pod的IP地址
nodeName: controlplane # Pod被调度到的节点
targetRef:
kind: Pod
name: nginx-7f456874f4-v8pnz
namespace: default
uid: b248209d-a854-48e8-8162-1abd4e1b498f
- ip: 192.168.1.3 # Pod的IP地址
nodeName: node01 # Pod被调度到的节点
targetRef:
kind: Pod
name: nginx-7f456874f4-c7224
namespace: default
uid: f45e4aa2-ddfd-48cd-a7d1-5bfb28d0f31f
ports:
- port: 80
protocol: TCPService与Endpoints、Pod的关系大体如下：
三、Service资源清单
yaml 格式的 Service 定义文件 ：kubectl get svc nginx -o yaml
apiVersion: v1 # 版本号
kind: Service # 资源类型，固定值Service
metadata: # 元数据
creationTimestamp: "2022-12-29T08:46:28Z"
labels: # 自定义标签属性列表
app: nginx # 标签：app=nginx
name: nginx # Service名称
namespace: default # Service所在的命名空间，默认值为default
resourceVersion: "2527"
uid: 1770ab42-bd33-4455-a190-5753e8eac460
spec:
clusterIP: 10.102.82.102 # 虚拟服务的IP地址，当spec.type=ClusterIP时，如果不指定，则系统进行自动分配，也可以手工指定。当spec.type=LoadBalancer时，则需要指定
clusterIPs:
- 10.102.82.102
externalTrafficPolicy: Cluster
internalTrafficPolicy: Cluster
ipFamilies:
- IPv4
ipFamilyPolicy: SingleStack
ports: # Service需要暴露的端口列表
- nodePort: 30314 # 当spec.type=NodePort时，指定映射到物理机的端口号
port: 80 # 服务监听的端口号
protocol: TCP # 端口协议，支持TCP和UDP，默认值为TCP
targetPort: 80 # 需要转发到后端Pod的端口号
selector: # label selector配置，将选择具有指定label标签的pod作为管理范围
app: nginx # 选择具有app=nginx的pod进行管理
sessionAffinity: None # session亲和性，可选值为ClientIP,表示将同一个源IP地址的客户端访问请求都转发到同一个后端Pod。默认值为空【None】
type: NodePort # Service的类型，指定service的访问方式，默认值为ClusterIP。取值范围：[ClusterIP、NodePort、LoadBalancer]
status:
loadBalancer: {} # 当spec.type=LoadBalancer时，设置外部负载均衡器的地址，用于公有云环境四、Service 类型
Service在k8s中有以下三种常用类型：
4.1、ClusterIP
只能在集群内部访问，默认类型，自动分配一个仅Cluster内部可以访问的虚拟IP（即VIP）。
4.2、NodePort
在每个主机节点上启用一个端口来暴露服务，可以在集群外部访问，也会分配一个稳定内部集群IP地址。
访问地址：<任意Node节点的IP地址>: NodePort端口
默认NodePort端口范围：30000-32767
4.3、LoadBalancer
与NodePort类似，在每个节点上启用一个端口来暴露服务。除此之外，Kubernetes会请求底层云平台（例如阿里云、腾讯云、AWS等）上的负载均衡器，将每个Node （[NodeIP]:[NodePort]）作为后端添加进去，此模式需要外部云环境的支持，适用于公有云。
4.4、ExternalName
ExternalName 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。
五、Service使用
5.1、ClusterIP
5.1.1、定义Pod资源清单
vim clusterip-pod.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx
spec:
replicas: 2
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 80
protocol: TCP5.1.2、创建Pod
$ kubectl apply -f clusterip-pod.yaml
deployment.apps/nginx created
$ kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-7f456874f4-c7224 1/1 Running 0 13s 192.168.1.3 node01 <none> <none>
nginx-7f456874f4-v8pnz 1/1 Running 0 13s 192.168.0.6 controlplane <none> <none>
# 任意节点发起请求
$ curl 192.168.1.3
<!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>
# 任意节点发起请求
$ curl 192.168.0.6
<!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>由于pod节点都是nginx默认界面都是一样的，为了方便测试，我们进入Pod修改默认界面：
$ kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-7f456874f4-c7224 1/1 Running 0 2m39s 192.168.1.3 node01 <none> <none>
nginx-7f456874f4-v8pnz 1/1 Running 0 2m39s 192.168.0.6 controlplane <none> <none>
$ kubectl exec -it nginx-7f456874f4-c7224 /bin/sh
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
# echo "hello, this request is from 192.168.1.3" > /usr/share/nginx/html/index.html
#
# cat /usr/share/nginx/html/index.html
hello, this request is from 192.168.1.3
# exit
$ kubectl exec -it nginx-7f456874f4-v8pnz /bin/sh
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
# echo "hello, this request is from 192.168.0.6" > /usr/share/nginx/html/index.html
# cat /usr/share/nginx/html/index.html
hello, this request is from 192.168.0.6
# exit
# 发起请求
$ curl 192.168.1.3
hello, this request is from 192.168.1.3
$ curl 192.168.0.6
hello, this request is from 192.168.0.65.1.3、定义Service资源清单
vim clusterip-svc.yaml
apiVersion: v1
kind: Service
metadata:
name: nginx
spec:
selector:
app: nginx
type: ClusterIP
# clusterIP: 10.109.113.53 # service IP地址 如果不写默认会生成一个
ports:
- port: 80 # service端口
targetPort: 80 # 目标pod端口5.1.4、创建Service
$ kubectl apply -f clusterip-svc.yaml
service/nginx created
$ kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 14d <none>
nginx ClusterIP 10.109.113.53 <none> 80/TCP 15s app=nginx
$ kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-7f456874f4-c7224 1/1 Running 0 11m 192.168.1.3 node01 <none> <none>
nginx-7f456874f4-v8pnz 1/1 Running 0 11m 192.168.0.6 controlplane <none> <none>
# 查看svc的详细描述信息，注意Endpoints表示的就是后端真实的Pod服务节点
$ kubectl describe svc nginx
Name: nginx
Namespace: default
Labels: <none>
Annotations: <none>
Selector: app=nginx
Type: ClusterIP
IP Family Policy: SingleStack
IP Families: IPv4
IP: 10.109.113.53
IPs: 10.109.113.53
Port: <unset> 80/TCP
TargetPort: 80/TCP
Endpoints: 192.168.0.6:80,192.168.1.3:80 # 后端真实的Pod服务节点【Pod的IP地址+虚端口】
Session Affinity: None
Events: <none>如上，我们可以看到，分配的ClusterIP为10.109.113.53，我们可以通过ClusterIP访问：
$ curl 10.109.113.53:80
hello, this request is from 192.168.0.6
$ curl 10.109.113.53:80
hello, this request is from 192.168.1.3可以看到，发起两次请求，请求会被负载均衡到两个不同的Pod，这就是Service提供的负载均衡功能。
5.2、NodePort
$ kubectl create deployment nginx --image=nginx
# 暴露端口，让集群外部可以访问，Service类型为NodePort
$ kubectl expose deployment nginx --port=80 --type=NodePort
service/nginx exposed
$ kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-748c667d99-5mf49 1/1 Running 0 6m13s 192.168.1.6 node01 <none> <none>
$ kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 14d <none>
nginx NodePort 10.98.224.65 <none> 80:31853/TCP 6m13s app=nginx可以看到，nginx这个service分配了一个ClusterIP为10.98.224.65，该Service的虚端口为80，K8S随机分配一个nodePort端口为31853，此时要访问nginx这个服务的话，有两种方式：
5.2.1、集群内通过ClusterIP+虚端口访问
# ClusterIP: 10.98.224.65 虚端口: 80
$ curl 10.98.224.65:80
<!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>5.2.2、集群外通过NodeIP+nodePort端口访问
# Node IP地址: 192.168.1.33 nodePort端口: 31853
$ curl 192.168.1.33:31853
<!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>5.2.3、集群内通过Pod IP + 虚端口访问
$ kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-748c667d99-5mf49 1/1 Running 0 11m 192.168.1.6 node01 <none> <none>
$ kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 14d <none>
nginx NodePort 10.98.224.65 <none> 80:31853/TCP 11m app=nginx
$ kubectl get ep
NAME ENDPOINTS AGE
kubernetes 172.30.1.2:6443 14d
nginx 192.168.1.6:80 11m
# Pod IP地址: 192.168.1.6 虚端口: 80
$ curl 192.168.1.6:80
<!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>5.3、ExternalName
创建ExternalName Service：
vim externalname-service.yaml：
apiVersion: v1
kind: Service
metadata:
name: externalname-service
spec:
type: ExternalName # Service类型为ExternalName
externalName: www.baidu.com$ kubectl apply -f externalname-service.yaml
service/externalname-service created
$ kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
externalname-service ExternalName <none> www.baidu.com <none> 7s <none>
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 17d <none>
$ kubectl describe svc externalname-service
Name: externalname-service
Namespace: default
Labels: <none>
Annotations: <none>
Selector: <none>
Type: ExternalName
IP Families: <none>
IP:
IPs: <none>
External Name: www.baidu.com
Session Affinity: None
Events: <none>
# 查看DNS域名解析
controlplane $ dig @10.96.0.10 externalname-service.default.svc.cluster.local
; <<>> DiG 9.16.1-Ubuntu <<>> @10.96.0.10 externalname-service.default.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: 31598
;; 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: 085781a8a4291b6d (echoed)
;; QUESTION SECTION:
;externalname-service.default.svc.cluster.local. IN A
;; ANSWER SECTION:
externalname-service.default.svc.cluster.local. 7 IN CNAME www.baidu.com.
www.baidu.com. 7 IN CNAME www.a.shifen.com.
www.a.shifen.com. 7 IN CNAME www.wshifen.com.
www.wshifen.com. 7 IN A 103.235.46.40
;; Query time: 4 msec
;; SERVER: 10.96.0.10#53(10.96.0.10)
;; WHEN: Mon Jan 09 09:43:29 UTC 2023
;; MSG SIZE rcvd: 279
六、Service代理模式
6.1、userspace 代理模式
在该模式下 kube-proxy 会为每一个 Service 创建一个监听端口，发送给 Cluseter IP 请求会被 iptable 重定向给 kube-proxy 监听的端口上，其中 kube-proxy 会根据 LB 算法将请求转发到相应的pod之上。
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。
6.2、iptables 代理模式
iptables模式下 kube-proxy 为每一个pod创建相对应的 iptables 规则，发送给 ClusterIP 的请求会被直接发送给后端pod之上。
在该模式下 kube-proxy 不承担负载均衡器的角色，其只会负责创建相应的转发策略，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。
6.3、IPVS 代理模式
IPVS模式与iptable模式类型，kube-proxy 会根据pod的变化创建相应的 IPVS转发规则，与iptalbes模式相比，IPVS模式工作在内核态，在同步代理规则时具有更好的性能，同时提高网络吞吐量为大型集群提供了更好的可扩展性，同时提供了大量的负责均衡算法。
注意：当 kube-proxy 以 IPVS 代理模式启动时，它将验证 IPVS 内核模块是否可用。 如果未检测到 IPVS 内核模块，则 kube-proxy 将退回到以 iptables 代理模式运行。
下面演示如何修改代理模式为IPVS代理模式。
6.3.1、加载ipvs相关内核模块
modprobe ip_vs
modprobe ip_vs_rr
modprobe ip_vs_wrr
modprobe ip_vs_sh6.3.2、编辑配置文件
实际上是修改kube-proxy对应的ConfingMap：
$ kubectl get cm -n kube-system | grep kube-proxy
NAME DATA AGE
kube-proxy 2 14d
$ kubectl edit cm kube-proxy -n kube-system
configmap/kube-proxy edited修改mode的值，将其修改为ipvs，如下图：
6.3.3、删除原有的kube-proxy代理
$ kubectl get pod -A | grep kube-proxy
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system kube-proxy-xnz4r 1/1 Running 0 14d
kube-system kube-proxy-zbxrb 1/1 Running 0 14d
$ kubectl delete pod kube-proxy-xnz4r -n kube-system
pod "kube-proxy-xnz4r" deleted
$ kubectl delete pod kube-proxy-zbxrb -n kube-system
pod "kube-proxy-zbxrb" deleted删除完成后，k8s会自动重启kube-proxy的Pod：
$ kubectl get pod -A | grep kube-proxy
kube-system kube-proxy-hvnmt 1/1 Running 0 6m35s
kube-system kube-proxy-zp6z5 1/1 Running 0 6m20s6.3.4、查看IPVS
$ 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
-> 172.30.1.2:6443 Masq 1 1 0
TCP 10.96.0.10:53 rr
-> 192.168.0.5:53 Masq 1 0 0
-> 192.168.1.2:53 Masq 1 0 0
TCP 10.96.0.10:9153 rr
-> 192.168.0.5:9153 Masq 1 0 0
-> 192.168.1.2:9153 Masq 1 0 0
TCP 10.99.58.167:80 rr
-> 192.168.0.6:80 Masq 1 0 0
-> 192.168.1.3:80 Masq 1 0 0
UDP 10.96.0.10:53 rr
-> 192.168.0.5:53 Masq 1 0 0
-> 192.168.1.2:53 Masq 1 0 0 
如上图，产生了一批转发规则。
七、HeadLiness services
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HeadLiness Service，这类Service不会分配Cluster IP，如果想要访问Service，只能通过Service的域名进行查询。
7.1、创建Pod
vim headliness-pod.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx
spec:
replicas: 2
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 80
protocol: TCP$ vim headliness-pod.yaml
$ kubectl apply -f headliness-pod.yaml
deployment.apps/nginx created
$ kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-7f456874f4-225j6 1/1 Running 0 16s 192.168.1.3 node01 <none> <none>
nginx-7f456874f4-r7csn 1/1 Running 0 16s 192.168.0.6 controlplane <none> <none>7.2、创建Service
vim headliness-service.yaml
apiVersion: v1
kind: Service
metadata:
name: headliness-service
spec:
selector:
app: nginx
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$ vim headliness-service.yaml
$ kubectl get pod -o wide --show-labels
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES LABELS
nginx-7f456874f4-225j6 1/1 Running 0 103s 192.168.1.3 node01 <none> <none> app=nginx,pod-template-hash=7f456874f4
nginx-7f456874f4-r7csn 1/1 Running 0 103s 192.168.0.6 controlplane <none> <none> app=nginx,pod-template-hash=7f456874f4
controlplane $ kubectl apply -f headliness-service.yaml
service/headliness-service created
controlplane $ kubectl get svc -o wide --show-labels
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR LABELS
headliness-service ClusterIP None <none> 80/TCP 10s app=nginx <none>
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 17d <none> component=apiserver,provider=kubernetes
# 查看详情
$ kubectl describe service headliness-service
Name: headliness-service
Namespace: default
Labels: <none>
Annotations: <none>
Selector: app=nginx
Type: ClusterIP
IP Family Policy: SingleStack
IP Families: IPv4
IP: None
IPs: None
Port: <unset> 80/TCP
TargetPort: 80/TCP
Endpoints: 192.168.0.6:80,192.168.1.3:80 # 能提供服务的Pod
Session Affinity: None
Events: <none>7.3、进入容器，查看服务域名
# 查看Pod
$ kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-7f456874f4-225j6 1/1 Running 0 4m37s 192.168.1.3 node01 <none> <none>
nginx-7f456874f4-r7csn 1/1 Running 0 4m37s 192.168.0.6 controlplane <none> <none>
# 进入Pod
$ kubectl exec nginx-7f456874f4-r7csn -it -- bin/bash
# 查看域名
root@nginx-7f456874f4-r7csn:/# cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.96.0.10
options ndots:5
# 通过Service的域名进行查询：默认访问规则service名称.名称空间.svc.cluster.local
# 在Pod内通过curl可以访问
root@nginx-7f456874f4-r7csn:/# curl headliness-service.default.svc.cluster.local
<!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>
root@nginx-7f456874f4-r7csn:/# exit
exit
# 查看DNS
$ apt install bind9-utils
$ dig @10.96.0.10 headliness-service.default.svc.cluster.local
; <<>> DiG 9.16.1-Ubuntu <<>> @10.96.0.10 headliness-service.default.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: 59994
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: b633b51a4ca3a653 (echoed)
;; QUESTION SECTION:
;headliness-service.default.svc.cluster.local. IN A
;; ANSWER SECTION:
headliness-service.default.svc.cluster.local. 30 IN A 192.168.1.3
headliness-service.default.svc.cluster.local. 30 IN A 192.168.0.6
;; Query time: 0 msec
;; SERVER: 10.96.0.10#53(10.96.0.10)
;; WHEN: Mon Jan 09 09:
