目录
一.service介绍
之前我们讲到的pod创建，里面有服务需要被集群内部访问或被外界访问，这样情况我们就需要借助service来为应用提供统一入口地址，他主要提供网络服务，将请求按负载均衡算法分发到各个容器。在访问时，pod的IP地址时会变化的，显然在pod提供稳定服务时不能通过IP地址去访问。
二.service参数详解
apiVersion: v1 #必写
kind: Service #必写
metadata: #必写
annotations: #自定义的注解属性列表
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"name":"my-nginx","namespace":"myns"},"spec":{"ports":[{"port":80,"protocol":"TCP","targetPort":80}],"selector":{"name":"my-nginx"}}}
creationTimestamp: "2023-12-02T01:18:01Z"
name: my-nginx #必写
namespace: myns #必写，建议和你创建pod和pod控制器的名称空间一致
resourceVersion: "1537"
uid: ab1bb8ce-be87-48d4-8396-5e802dfbca8c
spec: #必写
clusterIP: 10.109.39.11 #虚拟IP，当type=ClusterIP时设置，可以自己指定，也可以不写等系统自己分配
clusterIPs:
- 10.109.39.11
internalTrafficPolicy: Cluster
ipFamilies:
- IPv4
ipFamilyPolicy: SingleStack
ports: #端口暴露情况
- port: 80 #服务监听的端口
protocol: TCP #端口协议，默认TCP，支持TCP/UDP
targetPort: 80 #转发到后端pod的端口
nodePort: number #type=NodePort时设置，映射到主机的端口，可以自己指定也可以不写等系统分配，设置了type=NodePort，其他节点和外界就可以通过“此主机地址+这个端口号”进行访问
selector: #选择器，必写
name: my-nginx #注意一致性
sessionAffinity: None #是否支持session，默认none，也可以填写ClientIP,表示根据客户端IP来将同一个客户端请求分配到同一个pod
type: ClusterIP #类型选择，ClusterIP、NodePort、LoadBalancer，后面会详细介绍
status: #当type=LoadBalancer时这只，设置外部负载均衡器的地址（公有云环境），后面演示的时候介绍
loadBalancer: {}三.定义service的两种方式
1.命令行expose
这里创建一个关于nginx服务的3个副本数的pod，并且使用expose方式为其创建service，其中，--port=80指定nginx服务监听端口，--type=ClusterIP指定类型， --target-port=80指定转发到后端某端口，并使用暴露出来的IP进行访问验证是否成功。
[root@k8s-master service]# cat service1.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
name: my-nginx
name: my-nginx
namespace: myns
spec:
replicas: 3
selector:
matchLabels:
name: my-nginx
template:
metadata:
labels:
name: my-nginx
spec:
containers:
- name: my-nginx-pod
image: nginx
ports:
- containerPort: 80
[root@k8s-master service]# kubectl get pods -n myns
NAME READY STATUS RESTARTS AGE
my-nginx-7c787d8bb-g6fb5 1/1 Running 0 9s
my-nginx-7c787d8bb-t5jdh 1/1 Running 0 9s
my-nginx-7c787d8bb-znd22 1/1 Running 0 9s
[root@k8s-master service]# kubectl get deploy -n myns
NAME READY UP-TO-DATE AVAILABLE AGE
my-nginx 3/3 3 3 15s
[root@k8s-master service]# kubectl expose deployment my-nginx -n myns --port=80 --type=ClusterIP --target-port=80
service/my-nginx exposed
[root@k8s-master service]# kubectl get service -n myns #使用下方IP进行访问
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
my-nginx ClusterIP 10.111.4.81 <none> 80/TCP 6s
[root@k8s-master service]# curl 10.111.4.81
<!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@k8s-node1 ~]# curl 10.111.4.81 #在node1上访问，验证ClusterIP集群内部访问是否成功
<!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>2.yaml文件
这里在上面的deployment基础上继续配置service，ports部分和selector部分显得尤为重要，具体看代码注释
[root@k8s-master service]# cat service1.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
name: my-nginx
name: my-nginx
namespace: myns
spec:
replicas: 3
selector:
matchLabels:
name: my-nginx-deploy
template:
metadata:
labels:
name: my-nginx-deploy
spec:
containers:
- name: my-nginx-pod
image: nginx
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: my-nginx-service
namespace: myns
spec:
ports:
- protocol: TCP #TCP协议
targetPort: 80 #转发到后端pod的80端口
port: 80 #服务监听80端口
selector: #与deploy上面的模板进行匹配，表示为标签为name: my-nginx-deploy的pod开放服务
name: my-nginx-deploy
[root@k8s-master service]# kubectl apply -f service1.yaml
deployment.apps/my-nginx created
service/my-nginx-service created
[root@k8s-master service]# kubectl get service -n myns
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
my-nginx-service ClusterIP 10.98.64.75 <none> 80/TCP 7s
[root@k8s-master service]# curl 10.98.64.75
<!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>四.service负载均衡配置
1.kube-proxy代理模式
这里主要介绍ipvs代理，他实现从service到后端endpoint的负载分发任务，相较于旧版本的userspace和iptables来讲，ipvs具有更高的转发效率和吞吐率，也支持更多的负载均衡策略接下来介绍如何开启ipvs（之前介绍label那篇文章也讲到过），若不开启，会自动切换到iptables。
（1）设置ipvs
[root@k8s-master service]# lsmod | grep ip_vs #加载查看内核模块
ip_vs_sh 12688 0
ip_vs_wrr 12697 0
ip_vs_rr 12600 0
ip_vs 145458 6 ip_vs_rr,ip_vs_sh,ip_vs_wrr
nf_conntrack 139264 10 ip_vs,nf_nat,nf_nat_ipv4,nf_nat_ipv6,xt_conntrack,nf_nat_masquerade_ipv4,nf_nat_masquerade_ipv6,nf_conntrack_netlink,nf_conntrack_ipv4,nf_conntrack_ipv6
libcrc32c 12644 4 xfs,ip_vs,nf_nat,nf_conntrack
#将node部分改为ipvs
[root@k8s-master service]# kubectl edit configmap kube-proxy -n kube-system
configmap/kube-proxy edited
“
metricsBindAddress: ""
mode: "ipvs"
nodePortAddresses: null
oomScoreAdj: null
”
#删除kube-proxy的pod，自动重新拉取
[root@k8s-master service]# kubectl get pods -n kube-system | grep kube-proxy
kube-proxy-95q7f 1/1 Running 0 94m
kube-proxy-qf7wh 1/1 Running 0 92m
kube-proxy-rtg5c 1/1 Running 0 92m
[root@k8s-master service]# kubectl delete pod kube-proxy-95q7f kube-proxy-qf7wh kube-proxy-rtg5c -n kube-system
pod "kube-proxy-95q7f" deleted
pod "kube-proxy-qf7wh" deleted
pod "kube-proxy-rtg5c" deleted
[root@k8s-master service]# kubectl get pods -n kube-system | grep kube-proxy
kube-proxy-7b5fc 1/1 Running 0 6s
kube-proxy-pvv6k 1/1 Running 0 6s
kube-proxy-vbfnd 1/1 Running 0 6s
#验证生效
[root@k8s-master service]# kubectl logs kube-proxy-7b5fc -n kube-system | grep ipvs
I1202 02:44:06.831781 1 server_others.go:218] "Using ipvs Proxier"
[root@k8s-master service]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.2.150:30572 rr
-> 10.244.36.75:80 Masq 1 0 0
-> 10.244.169.147:80 Masq 1 0 0
-> 10.244.169.148:80 Masq 1 0 0
TCP 10.96.0.1:443 rr
-> 192.168.2.150:6443 Masq 1 1 0
TCP 10.96.0.10:53 rr
-> 10.244.235.193:53 Masq 1 0 0
-> 10.244.235.194:53 Masq 1 0 0
TCP 10.96.0.10:9153 rr
-> 10.244.235.193:9153 Masq 1 0 0
-> 10.244.235.194:9153 Masq 1 0 0
TCP 10.98.197.131:80 rr
-> 10.244.36.75:80 Masq 1 0 0
-> 10.244.169.147:80 Masq 1 0 0
-> 10.244.169.148:80 Masq 1 0 0
TCP 10.244.235.192:30572 rr
-> 10.244.36.75:80 Masq 1 0 0
-> 10.244.169.147:80 Masq 1 0 0
-> 10.244.169.148:80 Masq 1 0 0
UDP 10.96.0.10:53 rr
-> 10.244.235.193:53 Masq 1 0 0
-> 10.244.235.194:53 Masq 1 0 0 （2）负载均衡调度策略
rr（Round Robin）：轮询算法，将请求按照顺序依次分发给后端服务器。每个请求都按照先后顺序分配给下一个服务器，直到所有服务器都被分配到一个请求。然后再从头开始循环。
lc（Least Connections）：最小连接数算法，将请求分发给当前连接数最少的服务器。通过监视服务器上的活动连接数并选择最少连接的服务器，可以实现负载均衡。
dh（Destination Hashing）：目标哈希算法，根据请求的特定目标信息（例如源 IP 地址或会话 ID）计算哈希值，并将请求分发给与哈希值匹配的服务器。这样可以确保相同的请求始终被分发到相同的服务器上。
sh（Source Hashing）：源哈希算法，类似于目标哈希算法，但是使用源 IP 地址而不是目标信息来计算哈希值。这样可以确保来自同一来源的请求始终被发送到同一台服务器。
sed（Shortest Expected Delay）：最短期望延迟算法，根据每个服务器的预计延迟时间来选择服务器。该算法会考虑服务器的负载和延迟，并选择具有最短预计延迟的服务器来处理请求。
nq（Nginx Queue）：Nginx 队列算法(永不排队)，将请求放入队列中，并按照特定规则进行调度。这种算法通常与 Nginx 反向代理服务器一起使用，可以根据不同的规则（例如权重、连接数等）进行请求调度。
2.会话保持
通过sessionAffinity设置首次将客户端发起的请求发送某pod，之后的该客户端的请求都发往此pod，同时还可以配置timeoutSeconds:为其设置会话保持时间，详情见案例演示。
3.案例演示
没设置会话保持时，自动按照算法按照调度给3个pod（pod配置不同的页面以方面验证）
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
name: my-nginx
name: my-nginx
namespace: myns
spec:
replicas: 3
selector:
matchLabels:
name: my-nginx-deploy
template:
metadata:
labels:
name: my-nginx-deploy
spec:
containers:
- name: my-nginx-pod
image: nginx
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: my-nginx-service
namespace: myns
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
name: my-nginx-deploy
type: ClusterIP
[root@k8s-master service]# curl 10.107.18.89
pod3
[root@k8s-master service]# curl 10.107.18.89
pod2
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod3
[root@k8s-master service]# curl 10.107.18.89
pod2配置会话保持
[root@k8s-master service]# cat service1.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
name: my-nginx
name: my-nginx
namespace: myns
spec:
replicas: 3
selector:
matchLabels:
name: my-nginx-deploy
template:
metadata:
labels:
name: my-nginx-deploy
spec:
containers:
- name: my-nginx-pod
image: nginx
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: my-nginx-service
namespace: myns
spec:
sessionAffinity: ClientIP
sessionAffinityConfig:
clientIP:
timeoutSeconds: 10
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
name: my-nginx-deploy
type: ClusterIP
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod1
[root@k8s-master service]# curl 10.107.18.89
pod1五.四种Service类型
1.clusterip
上面已经讲到clusterip是集群内部访问类型，并且已经演示，接下来介绍其他类型
2.NodePort
这个类型使得服务不仅可以被集群内部访问，还可以被集群外部访问，nodeport暴露的是TCP4层，但会对集群节点主机端口产生占用，不适合大规模使用。需要注意的是：指定了类型为nodeport后，指定或自定暴露出来的端口的node的port（主机port），那么集群外部访问就需要使用node的ip（主机ip）+ node的port去访问。若是指定端口，应保持在30000-32767这个范围内。
[root@k8s-master service]# cat service1.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
name: my-nginx
name: my-nginx
namespace: myns
spec:
replicas: 3
selector:
matchLabels:
name: my-nginx-deploy
template:
metadata:
labels:
name: my-nginx-deploy
spec:
containers:
- name: my-nginx-pod
image: nginx
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: my-nginx-service
namespace: myns
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
nodePort: 30572 #指定暴露node上的端口
selector:
name: my-nginx-deploy
type: NodePort #指定类型
[root@k8s-master service]# kubectl apply -f service1.yaml
deployment.apps/my-nginx unchanged
service/my-nginx-service created
[root@k8s-master service]# kubectl get service -n myns
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
my-nginx-service NodePort 10.98.197.131 <none> 80:30572/TCP 9s
#如下，集群内部同样可以使用clusterip进行访问
[root@k8s-node1 ~]# curl 10.98.197.131
<!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>如下图，集群外部要使用主机地址+该端口进行访问
3.LoadBalancer
对外暴露服务的基础上又可以做负载均衡，LoadBalancer类型专属于云服务，可以动态分配网关，又可以分为 MetalLB 、PureLB 、OpenELB，之后的文章会讲述几类负载均衡器如何使用。
4.ExternalName
它允许将 Kubernetes 集群内部的服务映射到集群外部的服务地址。这种服务类型通常用于需要访问集群外部服务的情况，在 Pod 内部，你可以通过该 Service 的名称来进行访问，Kubernetes 会负责将请求路由到外部服务地址
[root@k8s-master service]# cat service2.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
name: my-nginx
name: my-nginx
namespace: myns
spec:
replicas: 3
selector:
matchLabels:
name: my-nginx-deploy
template:
metadata:
labels:
name: my-nginx-deploy
spec:
containers:
- name: my-nginx-pod
image: nginx
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: my-nginx-service
namespace: myns
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
name: my-nginx-deploy
type: ExternalName #指定类型为ExternalName
externalName: www.baidu.com #要访问的外部地址，可以是域名、IP等
[root@k8s-master service]# kubectl get pods -n myns
NAME READY STATUS RESTARTS AGE
my-nginx-5d67c8f488-48dsc 1/1 Running 0 19m
my-nginx-5d67c8f488-mn9qt 1/1 Running 0 19m
my-nginx-5d67c8f488-xgbgw 1/1 Running 0 19m
# nslookup my-nginx-service
Server: 10.96.0.10
Address: 10.96.0.10#53
my-nginx-service.myns.svc.cluster.local canonical name = www.baidu.com.
Name: www.baidu.com
Address: 39.156.66.14
Name: www.baidu.com
Address: 39.156.66.18
Name: www.baidu.com
Address: 2409:8c00:6c21:104f:0:ff:b03f:3ae
Name: www.baidu.com
Address: 2409:8c00:6c21:1051:0:ff:b0af:279a
# ping my-nginx-service
PING www.baidu.com (39.156.66.18): 56 data bytes
64 bytes from 39.156.66.18: icmp_seq=0 ttl=127 time=43.167 ms
64 bytes from 39.156.66.18: icmp_seq=1 ttl=127 time=147.273 ms
64 bytes from 39.156.66.18: icmp_seq=2 ttl=127 time=53.310 ms
^C--- www.baidu.com ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/stddev = 43.167/81.250/147.273/46.869 ms
