Service 暴露服務型別

通常情況下，我們會定義一個 Service 來管理一組 Pod 暴露相關的服務，如果要對外暴露服務的話，只需要定義相應的埠即可（NodePort模式），但如果定義了很多 Service 物件並暴露服務的話就需要配置很多埠，後續維護起來就會變的很複雜，所以 Kubernetes 中還使用了 Ingress 的機制，比如使用 Nginx 繫結一個固定埠 80，後續的請求通過轉發到 Service 即可。這樣如果每次新增服務的話，還需要修改 Nginx 的配置,為了解決這個問題 Kubernetes 中還使用了 Ingress Controller 元件。簡單理解就是原先需要修改 Nginx 配置，然後配置不同的轉發規則到 Service 這個過程抽象出來變成一個 Ingress 物件，後續 Nginx 的變更再通過 Ingress Controoler 與 Kubernetes API 互動，動態的去感知叢集中 Ingress 規則變化，再寫到 Nginx Pod 裡。

kind: Service
apiVersion: v1
metadata:
  name: test-service
spec:
  selector:
    app: test—-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080

由於 Service 中的服務僅可以在容器內部中通訊，如果需要外部能訪問到，還需要暴露 Service , 如下 ：

    internet
        |
  ------------
  [ Services ]

kubernetes 中定義瞭如下的一些服務型別：

Proxy

使用 Kubernetes 代理來訪問服務，一般內網檢視 dashboard，除錯遠端檢視時可能會用到。

{
  "kind": "Service",
  "apiVersion": "v1",
  "metadata": {
    "name": "kubernetes",
    "namespace": "default",
    "selfLink": "/api/v1/namespaces/default/services/kubernetes",
    "uid": "f594405b-dc19-11e8-90ea-0050569f4a19",
    "resourceVersion
 
": "6",
    "creationTimestamp": "2018-10-30T08:01:08Z",
    "labels": {
      "component": "apiserver",
      "provider": "kubernetes"
    }
  },
  "spec": {
    "ports": [
      {
        "name": "https",
        "protocol": "TCP",
        "port": 443,
        "targetPort": 6443
      }
    ],
    "clusterIP": "10.96.0.1",
    "type": "ClusterIP",
    "sessionAffinity": "None"
  },
  "status": {
    "loadBalancer": {}
  }
}

NodePort Service

指定服務型別為 NodePort 是將外部流量直接傳送給服務最原始的方式，需要在 Node 服務節點主機上開放特定的埠，通過繫結主機的某個埠,然後進行 Pod 的請求轉發和負載均衡，但這種方式下缺陷是 Service 可能有很多個，如果每個都繫結一個 Node 主機埠的話，主機需要開放外圍一堆的埠進行服務呼叫，管理混亂，並且只能使用 30000-32767 之間的埠，適用與臨時暴露某一個服務的埠演示的場景。

{
  "kind": "Service",
  "apiVersion": "v1",
  "metadata": {
    "name": "kubernetes-dashboard",
    "namespace": "kube-system",
    "selfLink": "/api/v1/namespaces/kube-system/services/kubernetes-dashboard",
    "uid": "edd78318-dc1a-11e8-90ea-0050569f4a19",
    "resourceVersion": "1076",
    "creationTimestamp": "2018-10-30T08:08:05Z",
    "labels": {
      "k8s-app": "kubernetes-dashboard"
    }
  },
  "spec": {
    "ports": [
      {
        "protocol": "TCP",
        "port": 443,
        "targetPort": 8443,
        "nodePort": 32151
      }
    ],
    "selector": {
      "k8s-app": "kubernetes-dashboard"
    },
    "clusterIP": "10.103.60.159",
    "type": "NodePort",
    "sessionAffinity": "None",
    "externalTrafficPolicy": "Cluster"
  },
  "status": {
    "loadBalancer": {}
  }
}

LoadBlancer Service

一般配合公用雲使用，指定的埠上的所有流量都將轉發到該服務，使用 LoadBlancer Service 暴露服務時實際上是向雲平臺申請建立一個負載均衡器來向外暴露服務，可能需要支付額外的費用。

Nginx Ingress Controller

Nginx Ingress Controller 是由 Nginx 與 Ingress Controller 兩部分組成。

Ingress

與上述的幾種型別不同，Ingress 實際上不是一種服務。它是位於多前面服務的不同，可以轉發不同的域名請求到叢集中不同的服務上，簡單的理解，Ingress 就是從 Kubernetes 叢集外訪問叢集的入口，將使用者的URL請求轉發到不同的 Service 上。Ingress 相當於 Nginx、Apache 等負載均衡方向代理伺服器，其中還包括規則定義，即 URL 的路由資訊，路由資訊得的重新整理由 Ingress controller 來提供。

Ingress controller

Ingress Controller 通過不斷地跟 kubernetes API 打交道，實時的感知後端 service、pod 等變化，比如新增和減少 pod，service 增加與減少等；當得到這些變化資訊後，Ingress Controller 再結合下文的 Ingress 生成配置，然後更新反向代理負載均衡器，並重新整理其配置，達到服務發現的作用。對於 Ingress controller 來說，建立一個 Ingress 相當於在 nginx.conf 中新增一個 server 入口，並 nginx -s reload 重新生效。。

比如想要通過負載均衡器實現不同子域名到不同服務的訪問：

foo.bar.com --|                 |-> foo.bar.com s1:80
              | 178.91.123.132  |
bar.foo.com --|                 |-> bar.foo.com s2:80

定義 Ingress

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: test
spec:
  rules:
  - host: foo.bar.com
    http:
      paths:
      - backend:
          serviceName: s1
          servicePort: 80
  - host: bar.foo.com
    http:
      paths:
      - backend:
          serviceName: s2
          servicePort: 80

Ingress本身並不會自動建立負載均衡器，需要執行一個 Ingress controller 來根據 Ingress 的定義來管理負載均衡器。為了 Ingress 正常工作，叢集中必須執行 Ingress controller ,支援 Ingress 的型別的 kube-controller 有如下幾種：

安裝 nginx-ingress-controller (host network 模式根據 Node 數量設定副本數，取決於部署的方式 Deployment or DaemonSet)

$ kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/mandatory.yaml
$ kubectl -n ingress-nginx get pod -o wide
NAME                                        READY   STATUS    RESTARTS   AGE   IP          NODE                NOMINATED NODE
nginx-ingress-controller-5bdbdc5657-bcn2f   1/1     Running   0          74m   10.38.0.1   kubernetes-node-2   <none>
nginx-ingress-controller-5bdbdc5657-mmtph   1/1     Running   0          79m   10.40.0.1   kubernetes-node-1   <none>
$ kubectl get pods --all-namespaces -l app.kubernetes.io/name=ingress-nginx --watch
NAMESPACE       NAME                                        READY   STATUS    RESTARTS   AGE
ingress-nginx   nginx-ingress-controller-6457d975c8-6twqf   1/1     Running   0          78m
ingress-nginx   nginx-ingress-controller-5bdbdc5657-mmtph   1/1     Running   0          83m

$ kubectl describe pod nginx-ingress-controller-6457d975c8-6twqf -n ingress-nginx
Name:               nginx-ingress-controller-6457d975c8-6twqf
Namespace:          ingress-nginx
Priority:           0
PriorityClassName:  <none>
Node:               kubernetes-node-2/172.23.216.50
Start Time:         Wed, 31 Oct 2018 20:04:44 +0800
Labels:             app.kubernetes.io/name=ingress-nginx
                    app.kubernetes.io/part-of=ingress-nginx
                    pod-template-hash=6457d975c8
Annotations:        prometheus.io/port: 10254
                    prometheus.io/scrape: true
Status:             Running
IP:                 172.23.216.50
Controlled By:      ReplicaSet/nginx-ingress-controller-6457d975c8
Containers:
  nginx-ingress-controller:
    Container ID:  docker://f4d5b69cf579752799d6d7e92c547ed9a5a0ba9154b3683c4956079ea9e77304
    Image:         quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.20.0
    Image ID:      docker-pullable://quay.io/kubernetes-ingress-controller/[email protected]:f6180c5397d2361c317aff1314dc192ab0f9f515346a5319422cdc264f05d2d9
    Ports:         80/TCP, 443/TCP
    Host Ports:    80/TCP, 443/TCP
    Args:
      /nginx-ingress-controller
      --configmap=$(POD_NAMESPACE)/nginx-configuration
      --publish-service=$(POD_NAMESPACE)/ingress-nginx
      --annotations-prefix=nginx.ingress.kubernetes.io
    State:          Running
      Started:      Wed, 31 Oct 2018 20:04:45 +0800
    Ready:          True
    Restart Count:  0
    Liveness:       http-get http://:10254/healthz delay=10s timeout=1s period=10s #success=1 #failure=3
    Readiness:      http-get http://:10254/healthz delay=0s timeout=1s period=10s #success=1 #failure=3
    Environment:
      POD_NAME:       nginx-ingress-controller-6457d975c8-6twqf (v1:metadata.name)
      POD_NAMESPACE:  ingress-nginx (v1:metadata.namespace)
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from nginx-ingress-serviceaccount-token-rhpsb (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  nginx-ingress-serviceaccount-token-rhpsb:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  nginx-ingress-serviceaccount-token-rhpsb
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type     Reason            Age                From                        Message
  ----     ------            ----               ----                        -------
  Warning  FailedScheduling  49m (x3 over 49m)  default-scheduler           0/3 nodes are available: 1 node(s) had taints that the pod didn't tolerate, 2 node(s) didn't have free ports for the requested pod ports.
  Normal   Scheduled         49m                default-scheduler           Successfully assigned ingress-nginx/nginx-ingress-controller-6457d975c8-6twqf to kubernetes-node-2
  Normal   Pulled            48m                kubelet, kubernetes-node-2  Container image "quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.20.0" already present on machine
  Normal   Created           48m                kubelet, kubernetes-node-2  Created container
  Normal   Started           48m                kubelet, kubernetes-node-2  Started container

檢視安裝的版本

POD_NAMESPACE=ingress-nginx
POD_NAME=$(kubectl get pods -n $POD_NAMESPACE -l app.kubernetes.io/name=ingress-nginx -o jsonpath='{.items[0].metadata.name}')
kubectl exec -it $POD_NAME -n $POD_NAMESPACE -- /nginx-ingress-controller --version

-------------------------------------------------------------------------------
NGINX Ingress controller
  Release:    0.20.0
  Build:      git-e8d8103
  Repository: https://github.com/kubernetes/ingress-nginx.git
-------------------------------------------------------------------------------

根據不同的網路環境與場景，需要選擇不同的策略，具體可以參考官方的文件，如下列舉常用的幾種：

Cloud environments 模式

如果是使用公有云，可以使用公有云的負載到 Node 節點即可，需要支付額外費用。

NodePort Service 模式（臨時測試,一般不建議使用）

apiVersion: v1
kind: Service
metadata:
  name: ingress-nginx
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  type: NodePort
  ports:
    - name: http
      port: 80
      targetPort: 80

# nodePort: 30000
      protocol: TCP
    - name: https
      port: 443
      targetPort: 443
      protocol: TCP
  selector:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx

---

執行

$ kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/provider/baremetal/service-nodeport.yaml
$ kubectl -n ingress-nginx get svc
NAME            TYPE       CLUSTER-IP    EXTERNAL-IP   PORT(S)                      AGE
ingress-nginx   NodePort   10.98.42.64   <none>        80:31460/TCP,443:31200/TCP   6m50s

host network 模式

修改 hostNetwork: true

vi nginx-ingress-controller.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx-ingress-controller
  namespace: ingress-nginx
  labels:
    app.kubernetes.io/name: ingress-nginx
    app.kubernetes.io/part-of: ingress-nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app.kubernetes.io/name: ingress-nginx
      app.kubernetes.io/part-of: ingress-nginx
  template:
    metadata:
      labels:
        app.kubernetes.io/name: ingress-nginx
        app.kubernetes.io/part-of: ingress-nginx
      annotations:
        prometheus.io/port: "10254"
        prometheus.io/scrape: "true"
    spec:
      hostNetwork: true
      serviceAccountName: nginx-ingress-serviceaccount
      containers:
        - name: nginx-ingress-controller
          image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.20.0
          args:
            - /nginx-ingress-controller
            - --configmap=$(POD_NAMESPACE)/nginx-configuration
            - --publish-service=$(POD_NAMESPACE)/ingress-nginx
            - --annotations-prefix=nginx.ingress.kubernetes.io
          securityContext:
            capabilities:
              drop:
                - ALL
              add:
                - NET_BIND_SERVICE
            # www-data -> 33
            runAsUser: 33
          env:
            - name: POD_NAME
              valueFrom:
                fieldRef:
                  fieldPath: metadata.name
            - name: POD_NAMESPACE
              valueFrom:
                fieldRef:
                  fieldPath: metadata.namespace
          ports:
            - name: http
              containerPort: 80
            - name: https
              containerPort: 443
          livenessProbe:
            failureThreshold: 3
            httpGet:
              path: /healthz
              port: 10254
              scheme: HTTP
            initialDelaySeconds: 10
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 1
          readinessProbe:
            failureThreshold: 3
            httpGet:
              path: /healthz
              port: 10254
              scheme: HTTP
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 1

---

$ kubectl apply -f nginx-ingress-controller.yaml

檢視 ingress-nginx

$ kubectl -n ingress-nginx get pod -o wide
NAME                                        READY   STATUS    RESTARTS   AGE    IP              NODE                NOMINATED NODE
nginx-ingress-controller-6457d975c8-6twqf   1/1     Running   0          3m7s   172.23.216.50   kubernetes-node-2   <none>
nginx-ingress-controller-6457d975c8-smjsv   1/1     Running   0          3m7s   172.23.216.49   kubernetes-node-1   <none>

測試訪問

$ curl -D- 172.23.216.50
HTTP/1.1 404 Not Found
Server: nginx/1.15.5
Date: Wed, 31 Oct 2018 12:08:40 GMT
Content-Type: text/html
Content-Length: 153
Connection: keep-alive

<html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>nginx/1.15.5</center>
</body>
</html>

建立 kubernetes-dashboard-ingress（預設 https ，annotations 頭必須設定 ）

vi kubernetes-dashboard-ingress.yaml

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: kubernetes-dashboard-ingress
  namespace: kube-system
  annotations:
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
    nginx.ingress.kubernetes.io/rewrite-target: /
    nginx.ingress.kubernetes.io/secure-backends: "true"

spec:
#  tls:
#   - secretName: k8s-dashboard-secret
  rules:
   - http:
      paths:
      - path: /
        backend:
          serviceName: kubernetes-dashboard
          servicePort: 443
      - path: /test
        backend:
          serviceName: test-nginx
          servicePort: 80

$ kubectl apply -f kubernetes-dashboard-ingress.yaml
$ kubectl get ingress -o wide --all-namespaces      
NAMESPACE     NAME                           HOSTS   ADDRESS   PORTS   AGE
kube-system   kubernetes-dashboard-ingress   *                 80      3h53m

備註：其他功能參考官方文件：

其他命令
#刪除 Ingress Controller 名稱空間
$ kubectl delete namespace nginx-ingress
#安裝網路元件
$ yum install net-tools
#檢視開放的埠
$ netstat -ntlp