在使用kubenetes的过程中，如何将服务开放到集群外部访问是一个重要的问题。当使用云平台（阿里云、腾讯云、AWS等）的容器服务时，我们可以通过配置 service 为 LoadBalancer 模式来绑定云平台的负载均衡器，从而实现外网的访问。但是，如果对于自建的 kubernetes裸机集群，这个问题则要麻烦的多。

祼机集群不支持负载均衡的方式，可用的不外乎NodePort、HostNetwork、ExternalIPs等方式来实现外部访问。但这些方式并不完美，他们或多或少都存在的一些缺点，这使得裸机集群成为Kubernetes生态系统中的二等公民。

MetalLB 旨在通过提供与标准网络设备集成的Network LB实施来解决这个痛点，从而使裸机群集上的外部服务也尽可能“正常运行”，减少运维上的管理成本。它是一种纯软件的解决方案，参考 https://kubernetes.github.io/ingress-nginx/deploy/baremetal/。

部署

创建namespace

$ kubectl create namespace metallb-system

2. 新建 secret

$ kubectl create secret generic -n metallb-system memberlist --from-literal=secretkey="$(openssl rand -base64 128)"

参数 from 前面是两个-

3. 部署

root@sxf-virtual-machine:~# kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/main/manifests/metallb.yaml 
Warning: policy/v1beta1 PodSecurityPolicy is deprecated in v1.21+, unavailable in v1.25+
podsecuritypolicy.policy/controller created
podsecuritypolicy.policy/speaker created
serviceaccount/controller created
serviceaccount/speaker created
clusterrole.rbac.authorization.k8s.io/metallb-system:controller created
clusterrole.rbac.authorization.k8s.io/metallb-system:speaker created
role.rbac.authorization.k8s.io/config-watcher created
role.rbac.authorization.k8s.io/pod-lister created
role.rbac.authorization.k8s.io/controller created
clusterrolebinding.rbac.authorization.k8s.io/metallb-system:controller created
clusterrolebinding.rbac.authorization.k8s.io/metallb-system:speaker created
rolebinding.rbac.authorization.k8s.io/config-watcher created
rolebinding.rbac.authorization.k8s.io/pod-lister created
rolebinding.rbac.authorization.k8s.io/controller created
daemonset.apps/speaker created
deployment.apps/controller created

查看部署结果

root@sxf-virtual-machine:~# kubectl get pod -n metallb-system
NAME                          READY   STATUS    RESTARTS   AGE
controller-6cc57c4567-cn766   1/1     Running   0          29m
speaker-4fv86                 1/1     Running   0          32m

root@sxf-virtual-machine:~# kubectl get sa -n metallb-system
NAME SECRETS AGE
controller 1 33m
default 1 33m
speaker 1 33m

配置 MetalLB

配置 MetalLB 为 Layer 2模式（使用 yaml 文件部署），文件 MetalLB-Layer2-Configmap.yaml

kind: ConfigMap
apiVersion: v1
metadata:
  name: config
  namespace: metallb-system
data:
  config: |
    address-pools:
    - name: default
      protocol: layer2
      addresses:
      - 192.168.3.251-192.168.3.254

这里配置一个由 MetalLB 二层模式控制的 service 外部 IP 段为 192.168.3.251 - 192.168.3.254。

还可以指定多个网段

addresses:
- 192.168.12.0/24
- 192.168.144.0/20

除了自动分配IP外，Metallb 还支持在定义服务的时候，通过 spec.loadBalancerIP 指定一个静态IP 。

$ kubectl apply -f MetalLB-Layer2-Configmap.yaml

使用kubectl log -f [matellb-contoller-pod]能看到配置更新过程

查看结果

root@sxf-virtual-machine:~# kubectl get cm -n metallb-system
NAME                 DATA   AGE
config               1      22s
kube-root-ca.crt     1      43m

测试

创建一个Nginx服务，服务类型为LoadBalancer：

deploy.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        ports:
        - name: http
          containerPort: 80

---
apiVersion: v1
kind: Service
metadata:
  name: nginx
spec:
  #loadBalancerIP: x.y.z.a  # 指定公网IP
  ports:
  - name: http
    port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: nginx
  type: LoadBalancer

服务创建，并查看服务信息：

$ kubectl apply -f deploy.yaml

查看pod

root@sxf-virtual-machine:~# kubectl get pod
NAME                    READY   STATUS    RESTARTS   AGE
nginx-8c9df995d-pvmkl   1/1     Running   0          2m10s

查看服务

root@sxf-virtual-machine:~# kubectl get svc -A
NAMESPACE      NAME                    TYPE           CLUSTER-IP       EXTERNAL-IP     PORT(S)                                                           AGE
default        details                 ClusterIP      10.110.60.221    <none>          9080/TCP                                                          3d1h
default        hostnames               ClusterIP      10.111.190.216   <none>          80/TCP                                                            3d1h
default        kubernetes              ClusterIP      10.96.0.1        <none>          443/TCP                                                           3d23h
default        nginx                   LoadBalancer   10.108.230.26    192.168.3.253   80:30829/TCP                                                      65s
default        productpage             ClusterIP      10.98.222.204    <none>          9080/TCP                                                          3d1h
default        ratings                 ClusterIP      10.104.86.58     <none>          9080/TCP                                                          3d1h
default        reviews                 ClusterIP      10.101.246.133   <none>          9080/TCP                                                          3d1h
istio-system   istio-eastwestgateway   LoadBalancer   10.99.130.139    192.168.3.252   15021:31544/TCP,15443:32575/TCP,15012:30747/TCP,15017:30099/TCP   3d
istio-system   istio-ingressgateway    LoadBalancer   10.96.196.70     192.168.3.251   15021:30035/TCP,80:31245/TCP,443:31639/TCP                        3d22h
istio-system   istiod                  ClusterIP      10.107.246.136   <none>          15010/TCP,15012/TCP,443/TCP,15014/TCP                             3d23h
kube-system    kube-dns                ClusterIP      10.96.0.10       <none>          53/UDP,53/TCP,9153/TCP                                            3d23h

这里就发现一些 LoadBalancer 类型的服务，被分配到了固定的 IP地址信息。

服务自动生成的 yaml 文件

root@sxf-virtual-machine:~# kubectl get svc nginx -o yaml
apiVersion: v1
kind: Service
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"name":"nginx","namespace":"default"},"spec":{"ports":[{"name":"http","port":80,"protocol":"TCP","targetPort":80}],"selector":{"app":"nginx"},"type":"LoadBalancer"}}
  creationTimestamp: "2021-09-29T11:26:35Z"
  name: nginx
  namespace: default
  resourceVersion: "1274438"
  uid: f2fb62dc-e277-4432-8496-2b5fb5984a55
spec:
  clusterIP: 10.108.230.26
  clusterIPs:
  - 10.108.230.26
  externalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - name: http
    nodePort: 30355
    port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: nginx
  sessionAffinity: None
  type: LoadBalancer
status:
  loadBalancer:
    ingress:
    - ip: 192.168.3.253

这时我们用 curl 192.168.3.253 验证一下nginx服务，就会发现返回了 Nginx 的欢迎信息。

root@sxf-virtual-machine:~# curl 192.168.3.253
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    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>

可以看到可以正常访问pod的内容。

剩下的就是我们如何使用了，经常部署方案是为集群服务创建一个 Ingress 的服务，参考 https://stackoverflow.com/questions/65789968/microk8s-metallb-ingress

最后我们清理pod

root@sxf-virtual-machine:~# kubectl delete -f deploy.yaml
deployment.apps "nginx" deleted
service "nginx" deleted

参考

除了本文介绍的 Metalldb 另，还有另一种解决方案为 openELB ，它是由国内互联网青云公司开源的一种方法，目前在 CNCF 沙盒在托管，已在国内不少企业如本来生活、苏州电视台、视源股份、云智天下、Jollychic、QingCloud、百旺、Rocketbyte 等海内外多家企业采用。

学习笔记

Web系统架构 Golang Lamp Nginx MySQL

k8s安装负载均衡器：Metallb

部署

测试

参考