Service 的概念
Kubernetes Service
定义了这样一种抽象:一个 Pod
的逻辑分组,一种可以访问它们的策略 —— 通常称为微服务。 这一组 Pod
能够被 Service
访问到,通常是通过 Label Selector
Service能够提供负载均衡的能力,但是在使用上有以下限制:
- 只提供 4 层负载均衡能力,而没有 7 层功能,但有时我们可能需要更多的匹配规则来转发请求,这点上 4 层负载均衡是不支持的
Service 的类型
Service 在 K8s 中有以下四种类型:
- ClusterIp :默认类型,自动分配一个仅 Cluster 内部可以访问的虚拟 IP
- NodePort:在 ClusterIP 基础上为 Service 在每台机器上绑定一个端口,这样就可以通过 : NodePort 来访问该服务
- LoadBalancer:在 NodePort 的基础上,借助 cloud provider 创建一个外部负载均衡器,并将请求转发到:NodePort
- ExternalName:把集群外部的服务引入到集群内部来,在集群内部直接使用。没有任何类型代理被创建,这只有 kubernetes 1.7 或更高版本的 kube-dns 才支持
VIP 和 Service 代理
在 Kubernetes 集群中,每个 Node 运行一个 kube-proxy
进程。 kube-proxy
负责为 Service
实现了一种 VIP (虚拟 IP)的形式,而不是 ExternalName
的形式。 在 Kubernetes v1.0 版本,代理完全在 userspace。在Kubernetes v1.1 版本,新增了 iptables 代理,但并不是默认的运行模式。 从 Kubernetes v1.2 起,默认就是iptables 代理。 在 Kubernetes v1.8.0-beta.0 中,添加了 ipvs 代理
在 Kubernetes 1.14 版本开始默认使用 ipvs 代理
在 Kubernetes v1.0 版本, Service
是 “4层”(TCP/UDP over IP)概念。 在 Kubernetes v1.1 版本,新增了Ingress
API (beta 版),用来表示 “7层”(HTTP)服务
代理模式的分类
Ⅰ、userspace 代理模式
Ⅱ、iptables 代理模式
Ⅲ、* ipvs 代理模式
这种模式,kube-proxy 会监视 Kubernetes Service
对象和 Endpoints ,调用 netlink 接口以相应地创建 ipvs 规则并定期与 Kubernetes Service 对象和 Endpoints 对象同步 ipvs 规则,以确保 ipvs 状态与期望一致。访问服务时,流量将被重定向到其中一个后端 Pod
与 iptables 类似,ipvs 于 netfilter 的 hook 功能,但使用哈希表作为底层数据结构并在内核空间中工作。这意味着 ipvs 可以更快地重定向流量,并且在同步代理规则时具有更好的性能。此外,ipvs 为负载均衡算法提供了更多选项,例如:
rr
:轮询调度lc
:最小连接数dh
:目标哈希sh
:源哈希sed
:最短期望延迟nq
: 不排队调度
示例说明
ClusterIP
clusterIP 主要在每个 node 节点使用 iptables ,将发向 clusterIP 对应端口的数据,转发到 kube-proxy 中。然后 kube-proxy 自己内部实现有负载均衡的方法,并可以查询到这个 service 下对应 pod 的地址和端口,进而把数据转发给对应的 pod 的地址和端口
为了实现图上的功能,主要需要以下几个组件的协同工作:
- apiserver 用户通过 kubectl 命令向 apiserver 发送创建 service 的命令,apiserver 接收到请求后将数据存储到 etcd中
- kube-proxy kubernetes 的每个节点中都有一个叫做 kube-porxy 的进程,这个进程负责感知 service,pod 的变化,并将变化的信息写入本地的 iptables 规则中
- iptables 使用 NAT 等技术将 virtualIP 的流量转至 endpoint 中
创建 svc-deployment.yaml
cat <<EOF >./svc-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: myapp-deployment
namespace: default
spec:
replicas: 3
selector:
matchLabels:
app: myapp
release: stabel
template:
metadata:
labels:
app: myapp
release: stabel
env: test
spec:
containers:
- name: myapp
image: hub.yangguoxiang.com/library/myapp:v2.0
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort: 80
EOF
kubectl apply -f svc-deployment.yaml
创建 Service 信息
cat <<EOF >./svc-service.yaml
apiVersion: v1
kind: Service
metadata:
name: myapp
namespace: default
spec:
type: ClusterIP
selector:
app: myapp
release: stabel
ports:
- name: http
port: 80
targetPort: 80
EOF
$ kubectl apply -f svc-service.yaml
service/myapp created
$ 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
-> 192.168.5.80:6443 Masq 1 3 0
TCP 10.103.202.179:80 rr
-> 10.244.1.63:80 Masq 1 0 0
-> 10.244.1.64:80 Masq 1 0 0
-> 10.244.2.52:80 Masq 1 0 0
$ curl 10.103.202.179:80/hostname.html
myapp-deployment-55c4f54f54-gl6fj
$ curl 10.103.202.179:80/hostname.html
myapp-deployment-55c4f54f54-wvcgf
Headless Service
无头服务,也是中特殊的 ClusterIP
有时不需要或不想要负载均衡,以及单独的 Service IP 。遇到这种情况,可以通过指定 Cluster IP( .spec.clusterIP
) 的值为 “None” 来创建 Headless Service 。这类 Service 并不会分配 Cluster IP , kube-proxy 不会处理它们,而且平台也不会为它们进行负载均衡和路由
cat <<EOF >./myapp-headless.yaml
apiVersion: v1
kind: Service
metadata:
name: myapp-headless
namespace: default
spec:
selector:
app: myapp
clusterIP: "None"
ports:
- port: 80
targetPort: 80
EOF
$ kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
myapp-headless ClusterIP None <none> 80/TCP 52s
# # 下载 dig 命令
$ yum -y install bind-utils
$ kubectl get pod -n kube-system -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
coredns-5c98db65d4-8csxj 1/1 Running 10 6d3h 10.244.0.18 k8s-master01 <none> <none>
coredns-5c98db65d4-lnddr 1/1 Running 11 6d3h 10.244.0.19 k8s-master01 <none> <none>
$ dig -t A myapp-headless.default.svc.cluster.local. @10.244.0.18
...
;; ANSWER SECTION:
myapp-headless.default.svc.cluster.local. 30 IN A 10.244.2.52
myapp-headless.default.svc.cluster.local. 30 IN A 10.244.1.63
myapp-headless.default.svc.cluster.local. 30 IN A 10.244.1.64
...
$ kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
myapp-deployment-55c4f54f54-gl6fj 1/1 Running 0 25m 10.244.2.52 k8s-node02 <none> <none>
myapp-deployment-55c4f54f54-wmmzm 1/1 Running 0 25m 10.244.1.63 k8s-node01 <none> <none>
myapp-deployment-55c4f54f54-wvcgf 1/1 Running 0 25m 10.244.1.64 k8s-node01 <none> <none>
NodePort
NodePort 的原理在于在 node 上开了一个端口,将向该端口的流量导入到 kube-proxy ,然后由 kube-proxy 进一步到给对应的 pod
cat <<EOF >./nodePort.yaml
apiVersion: v1
kind: Service
metadata:
name: myapp
namespace: default
spec:
type: NodePort
selector:
app: myapp
release: stabel
ports:
- name: http
port: 80
targetPort: 80
EOF
测试操作命令
$ kubectl apply -f nodePort.yaml
service/myapp created
$ kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 6d3h
myapp NodePort 10.99.47.212 <none> 80:32547/TCP 9s
# # 80 本地固定端口 32547 随机分配外部可访问每个节点的端口
$ ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.5.80:32547 rr
-> 10.244.1.63:80 Masq 1 0 0
-> 10.244.1.64:80 Masq 1 0 0
-> 10.244.2.52:80 Masq 1 0 0
TCP 10.99.47.212:80 rr
-> 10.244.1.63:80 Masq 1 0 0
-> 10.244.1.64:80 Masq 1 0 0
-> 10.244.2.52:80 Masq 1 0 0
$ curl 10.99.47.212/hostname.html
myapp-deployment-55c4f54f54-gl6fj
$ iptables -t nat -nvL
KUBE-NODEPORTS
LoadBalancer
云服务负载,收费服务
loadBalancer 和 nodePort 其实是同一种方式。区别在于 loadBalancer 比 nodePort 多了一步,就是可以调用 cloud provider 去创建 LB 来向节点导流
ExternalName
做DNS映射,将外部地址引入内部使用
这种类型的 Service 通过返回 CNAME 和它的值,可以将服务映射到 externalName 字段的内容( 例如:hub.yangguoxiang.com )。ExternalName Service 是 Service 的特例,它没有 selector ,也没有定义任何的端口和
Endpoint。相反的,对于运行在集群外部的服务,它通过返回该外部服务的别名这种方式来提供服务
cat <<EOF >./externalName.yaml
kind: Service
apiVersion: v1
metadata:
name: my-service-1
namespace: default
spec:
type: ExternalName
externalName: hub.yangguoxiang.com
EOF
$ kubectl create -f externalName.yaml
service/my-service-1 created
$ kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 6d4h
my-service-1 ExternalName <none> hub.yangguoxiang.com <none> 26s
myapp NodePort 10.99.47.212 <none> 80:32547/TCP 16m
$ dig -t A my-service-1.default.svc.cluster.local. @10.244.0.18
...
;; ANSWER SECTION:
my-service-1.default.svc.cluster.local. 30 IN CNAME hub.yangguoxiang.com.
...
当查询主机 my-service.defalut.svc.cluster.local ( SVC_NAME.NAMESPACE.svc.cluster.local )时,集群的 DNS 服务将返回一个值 my.database.example.com 的 CNAME 记录。访问这个服务的工作方式和其他的相同,唯一不同的是重定向发生在 DNS 层,而且不会进行代理或转发
Ingree
资料信息
Ingress-Nginx github 地址:https://github.com/kubernetes/ingress-nginx Ingress-Nginx 官方网站:https://kubernetes.github.io/ingress-nginx/
nginx-ingress
导入 nginx-ingress 镜像
# # 国外服务器,网络快,直接 pull
[root@k8s-node01 ~]$ docker pull quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.25.0
# # 国内服务器,网络慢,导入镜像
[root@k8s-node01 ~]$ tar -zxvf ingree.contro.tar.gz
ingree.contro.tar
[root@k8s-node01 ~]$ docker load -i ingree.contro.tar
...
Loaded image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.25.0
部署 Ingress-Nginx
$ cd /root/install-k8s/plugin/ingress
$ wget https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/mandatory.yaml
$ kubectl apply -f mandatory.yaml
...
deployment.apps/nginx-ingress-controller created
# # 查看状态
$ kubectl get pod -n ingress-nginx
NAME READY STATUS RESTARTS AGE
nginx-ingress-controller-799dbf6fbd-nhz6z 0/1 ContainerCreating 0 7m38s
# # 查看未成功启动原因,发现从 quay.io 仓库拉取镜像过慢卡死
$ kubectl describe pod nginx-ingress-controller-799dbf6fbd-nhz6z -n ingress-nginx
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 2m41s default-scheduler Successfully assigned ingress-nginx/nginx-ingress-controller-799dbf6fbd-glzct to k8s-node02
Normal Pulling 2m40s kubelet, k8s-node02 Pulling image "quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.26.1"
# # 修改仓库地址 (mandatory.yaml)
image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.26.1
修改为:
image: quay-mirror.qiniu.com/kubernetes-ingress-controller/nginx-ingress-controller:0.26.1
$ wget https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/provider/baremetal/service-nodeport.yaml
$ kubectl apply -f service-nodeport.yaml
service/ingress-nginx created
$ kubectl get svc -n ingress-nginx
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
ingress-nginx NodePort 10.99.146.64 <none> 80:31199/TCP,443:31263/TCP 60s
Ingress HTTP 代理访问
cat <<EOF >./ingress-http-dm-svc.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx-dm
spec:
replicas: 2
template:
metadata:
labels:
name: nginx
spec:
containers:
- name: nginx
image: hub.yangguoxiang.com/library/myapp:v1.0
imagePullPolicy: IfNotPresent
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: nginx-svc
spec:
ports:
- port: 80
targetPort: 80
protocol: TCP
selector:
name: nginx
EOF
$ kubectl apply -f ./ingress-http-dm-svc.yaml
deployment.extensions/nginx-dm created
service/nginx-svc created
cat <<EOF >./ingress-http-ingress.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: nginx-test
spec:
rules:
- host: www1.yangguoxiang.com
http:
paths:
- path: /
backend:
serviceName: nginx-svc
servicePort: 80
EOF
$ kubectl apply -f ./ingress-http-ingress.yaml
ingress.extensions/nginx-test created
测试
$ kubectl get svc -n ingress-nginx
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
ingress-nginx NodePort 10.110.159.163 <none> 80:30521/TCP,443:32024/TCP 34m
在宿主机配置hostname映射:192.168.5.80 www1.yangguoxiang.com
访问地址:http://www1.yangguoxiang.com:30521/hostname.html
详细示例见 示例说明 -> Ingress HTTP 代理示例
Ingress HTTPS 代理访问
创建证书,以及 cert 存储方式
$ openssl req -x509 -sha256 -nodes -days 365 \
-newkey rsa:2048 -keyout tls.key -out tls.crt \
-subj "/CN=nginxsvc/O=nginxsvc"
$ kubectl create secret tls tls-secret --key tls.key --cert tls.crt
cat <<EOF >./nginx-ingress-https.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: nginx-ingress-https
spec:
tls:
- hosts:
- www3.yangguoxiang.com
secretName: tls-secret
rules:
- host: www3.yangguoxiang.com
http:
paths:
- path: /
backend:
serviceName: nginx-svc-3
servicePort: 80
EOF
详细示例见 示例说明 -> Ingress HTTPS 代理示例
Nginx 进行 BasicAuth
$ yum -y install httpd
$ htpasswd -c auth foo
输入密码:123456
确认密码:123456
$ kubectl create secret generic basic-auth --from-file=auth
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: ingress-with-auth
annotations:
nginx.ingress.kubernetes.io/auth-type: basic
nginx.ingress.kubernetes.io/auth-secret: basic-auth
nginx.ingress.kubernetes.io/auth-realm: 'Authentication Required - foo'
spec:
rules:
- host: auth.yangguoxiang.com
http:
paths:
- path: /
backend:
serviceName: nginx-svc-1
servicePort: 80
$ kubectl get svc -n ingress-nginx
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
ingress-nginx NodePort 10.110.159.163 <none> 80:30521/TCP,443:32024/TCP 102m
访问http:http://auth.yangguoxiang.com:30521/
返回:Hello MyApp | Version: 1.0 | Pod Name
认证账号:foo
密码:123456(前面创建时设定的)
Nginx 进行重写
名称 | 描述 | 值 |
---|---|---|
nginx.ingress.kubernetes.io/rewrite-target | 必须重定向流量的目标URI | 串 |
nginx.ingress.kubernetes.io/ssl-redirect | 指示位置部分是否仅可访问SSL(当Ingress包含证书时默认为True) | 布尔 |
nginx.ingress.kubernetes.io/force-ssl-redirect | 即使Ingress未启用TLS,也强制重定向到HTTPS | 布尔 |
nginx.ingress.kubernetes.io/app-root | 定义Controller必须重定向的应用程序根,如果它在’/‘上下文中 | 串 |
nginx.ingress.kubernetes.io/use-regex | 指示Ingress上定义的路径是否使用正则表达式 | 布尔 |
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: nginx-test
annotations:
nginx.ingress.kubernetes.io/rewrite-target: https://www3.yangguoxiang.com:32024
spec:
rules:
- host: re.yangguoxiang.com
http:
paths:
- path: /
backend:
serviceName: nginx-svc-1
servicePort: 80
访问:http://re.yangguoxiang.com:30521
跳转:https://www3.yangguoxiang.com:32024
返回:Hello MyApp | Version: 1.0 | Pod Name
示例说明
Ingress HTTP 代理示例
网络设计图:
cat <<EOF >./nginx-dm-1.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx-dm-1
spec:
replicas: 2
template:
metadata:
labels:
name: nginx-1
spec:
containers:
- name: nginx-1
image: hub.yangguoxiang.com/library/myapp:v1.0
imagePullPolicy: IfNotPresent
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: nginx-svc-1
spec:
ports:
- port: 80
targetPort: 80
protocol: TCP
selector:
name: nginx-1
EOF
cat <<EOF >./nginx-dm-2.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx-dm-2
spec:
replicas: 2
template:
metadata:
labels:
name: nginx-2
spec:
containers:
- name: nginx-2
image: hub.yangguoxiang.com/library/myapp:v2.0
imagePullPolicy: IfNotPresent
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: nginx-svc-2
spec:
ports:
- port: 80
targetPort: 80
protocol: TCP
selector:
name: nginx-2
EOF
cat <<EOF >./nginx-ingress.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: nginx-ingress-1
spec:
rules:
- host: www1.yangguoxiang.com
http:
paths:
- path: /
backend:
serviceName: nginx-svc-1
servicePort: 80
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: nginx-ingress-2
spec:
rules:
- host: www2.yangguoxiang.com
http:
paths:
- path: /
backend:
serviceName: nginx-svc-2
servicePort: 80
EOF
$ kubectl apply -f nginx-dm-1.yaml
deployment.extensions/nginx-dm-1 created
service/nginx-svc-1 created
$ kubectl apply -f nginx-dm-2.yaml
deployment.extensions/nginx-dm-2 created
service/nginx-svc-2 created
$ kubectl apply -f nginx-ingress.yaml
ingress.extensions/nginx-ingress-1 created
ingress.extensions/nginx-ingress-2 created
$ kubectl get pod -n ingress-nginx
NAME READY STATUS RESTARTS AGE
nginx-ingress-controller-6dc8b6fc95-mvw6s 1/1 Running 0 94m
$ kubectl exec -it nginx-ingress-controller-6dc8b6fc95-mvw6s -n ingress-nginx -- /bin/bash
/etc/nginx$ cat nginx.conf | grep 'www1' -A 30
$ kubectl get svc -n ingress-nginx
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
ingress-nginx NodePort 10.110.159.163 <none> 80:30521/TCP,443:32024/TCP 102m
访问:http://www1.yangguoxiang.com:30521/
返回:Hello MyApp | Version: 1.0 | Pod Name
访问:http://www2.yangguoxiang.com:30521/
返回:Hello MyApp | Version: 2.0 | Pod Name
Ingress HTTPS 代理示例
基于 Ingress HTTP 示例继续
创建证书
$ openssl req -x509 -sha256 -nodes -days 365 \
-newkey rsa:2048 -keyout tls.key -out tls.crt \
-subj "/CN=nginxsvc/O=nginxsvc"
$ kubectl create secret tls tls-secret --key tls.key --cert tls.crt
cat <<EOF >./nginx-dm-3.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: nginx-dm-3
spec:
replicas: 2
template:
metadata:
labels:
name: nginx-3
spec:
containers:
- name: nginx-3
image: hub.yangguoxiang.com/library/myapp:v3.0
imagePullPolicy: IfNotPresent
ports:
- containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
name: nginx-svc-3
spec:
ports:
- port: 80
targetPort: 80
protocol: TCP
selector:
name: nginx-3
EOF
cat <<EOF >./nginx-ingress-https.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: nginx-ingress-https
spec:
tls:
- hosts:
- www3.yangguoxiang.com
secretName: tls-secret
rules:
- host: www3.yangguoxiang.com
http:
paths:
- path: /
backend:
serviceName: nginx-svc-3
servicePort: 80
EOF
$ kubectl apply -f nginx-dm-3.yaml
deployment.extensions/nginx-dm-3 created
service/nginx-svc-3 created
$ kubectl apply -f nginx-ingress-https.yaml
ingress.extensions/nginx-ingress-https created
$ kubectl get svc -n ingress-nginx
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
ingress-nginx NodePort 10.110.159.163 <none> 80:30521/TCP,443:32024/TCP 102m
访问https:https://www3.yangguoxiang.com:32024/
返回:Hello MyApp | Version: 3.0 | Pod Name
访问http:http://www3.yangguoxiang.com:30521/
返回:Hello MyApp | Version: 3.0 | Pod Name