11、Kubernetes核心技术 - Service
目录
一、概述
二、Endpoint
三、Service资源清单
四、Service 类型
4.1、ClusterIP
4.2、NodePort
4.3、LoadBalancer
4.4、ExternalName
五、Service使用
5.1、ClusterIP
5.1.1、定义Pod资源清单
5.1.2、创建Pod
5.1.3、定义Service资源清单
5.1.4、创建Service
5.2、NodePort
5.2.1、集群内通过ClusterIP+虚端口访问
5.2.2、集群外通过NodeIP+nodePort端口访问
5.2.3、集群内通过Pod IP + 虚端口访问
5.3、ExternalName
六、Service代理模式
6.1、userspace 代理模式
6.2、iptables 代理模式
6.3、IPVS 代理模式
6.3.1、加载ipvs相关内核模块
6.3.2、编辑配置文件
6.3.3、删除原有的kube-proxy代理
6.3.4、查看IPVS
七、HeadLiness services
7.1、创建Pod
7.2、创建Service
7.3、进入容器，查看服务域名
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 app=nginx,pod-template-hash=7f456874f4
nginx-7f456874f4-v8pnz 1/1 Running 0 20m 192.168.0.6 controlplane app=nginx,pod-template-hash=7f456874f4
$ kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 443/TCP 14d
nginx ClusterIP 10.109.113.53 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: TCP Service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
nginx-7f456874f4-v8pnz 1/1 Running 0 13s 192.168.0.6 controlplane
# 任意节点发起请求
$ curl 192.168.1.3
Welcome to nginx!
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.
For online documentation and support please refer to
nginx.org.
Commercial support is available at
nginx.com.
Thank you for using nginx.
# 任意节点发起请求
$ curl 192.168.0.6
Welcome to nginx!
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.
For online documentation and support please refer to
nginx.org.
Commercial support is available at
nginx.com.
Thank you for using nginx.
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
nginx-7f456874f4-v8pnz 1/1 Running 0 2m39s 192.168.0.6 controlplane
$ 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 192.168.0.6 5.1.3、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 10.96.0.1 443/TCP 14d
nginx ClusterIP 10.109.113.53 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
nginx-7f456874f4-v8pnz 1/1 Running 0 11m 192.168.0.6 controlplane
# 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:
Annotations:
Selector: app=nginx
Type: ClusterIP
IP Family Policy: SingleStack
IP Families: IPv4
IP: 10.109.113.53
IPs: 10.109.113.53
Port: 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: 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
$ kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 443/TCP 14d
nginx NodePort 10.98.224.65 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
Welcome to nginx!
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.
For online documentation and support please refer to
nginx.org.
Commercial support is available at
nginx.com.
Thank you for using nginx.
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
Welcome to nginx!
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.
For online documentation and support please refer to
nginx.org.
Commercial support is available at
nginx.com.
Thank you for using nginx.
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
$ kubectl get svc -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.96.0.1 443/TCP 14d
nginx NodePort 10.98.224.65 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
Welcome to nginx!
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.
For online documentation and support please refer to
nginx.org.
Commercial support is available at
nginx.com.
Thank you for using nginx.
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 www.baidu.com 7s
kubernetes ClusterIP 10.96.0.1 443/TCP 17d
$ kubectl describe svc externalname-service
Name: externalname-service
Namespace: default
Labels:
Annotations:
Selector:
Type: ExternalName
IP Families:
IP:
IPs:
External Name: www.baidu.com
Session Affinity: None
Events:
# 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
nginx-7f456874f4-r7csn 1/1 Running 0 16s 192.168.0.6 controlplane 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 app=nginx,pod-template-hash=7f456874f4
nginx-7f456874f4-r7csn 1/1 Running 0 103s 192.168.0.6 controlplane 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 80/TCP 10s app=nginx
kubernetes ClusterIP 10.96.0.1 443/TCP 17d component=apiserver,provider=kubernetes
# 查看详情
$ kubectl describe service headliness-service
Name: headliness-service
Namespace: default
Labels:
Annotations:
Selector: app=nginx
Type: ClusterIP
IP Family Policy: SingleStack
IP Families: IPv4
IP: None
IPs: None
Port: 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: 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
nginx-7f456874f4-r7csn 1/1 Running 0 4m37s 192.168.0.6 controlplane
# 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
Welcome to nginx!
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.
For online documentation and support please refer to
nginx.org.
Commercial support is available at
nginx.com.
Thank you for using nginx.
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: 