docker - Kubernetes 节点无法访问外部 Kafka 集群

Question

我有一个 Kubernetes 集群，其中包含多个需要连接到远程 Kafka 集群的 java 微服务。服务器位于 DigitalOcean 中，可在其专用网络中完全访问。 Kafka 集群不使用 Kubernetes，它不在集群内。

我使用 kubeadm 启动了整个集群，这是关于集群的信息:

# kubectl cluster-info
Kubernetes master is running at https://10.132.113.68:6443
KubeDNS is running at https://10.132.113.68:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

集群版本

# kubectl version
Client Version: version.Info{Major:"1", Minor:"10", GitVersion:"v1.10.2", GitCommit:"81753b10df112992bf51bbc2c2f85208aad78335", GitTreeState:"clean", BuildDate:"2018-04-27T09:22:21Z", GoVersion:"go1.9.3", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.7", GitCommit:"dd5e1a2978fd0b97d9b78e1564398aeea7e7fe92", GitTreeState:"clean", BuildDate:"2018-04-18T23:58:35Z", GoVersion:"go1.9.3", Compiler:"gc", Platform:"linux/amd64"}

这用于设置网络:

kubeadm init --pod-network-cidr=10.244.0.0/16 --apiserver-advertise-address=10.132.113.68 --kubernetes-version stable-1.8

所有 pod 都成功启动:

# kubectl get pods --all-namespaces
NAMESPACE     NAME                                                        READY     STATUS      RESTARTS   AGE
default       datadog-agent-5cht2                                         1/1       Running     0          12d
default       datadog-agent-5r7rw                                         1/1       Running     0          12d
default       datadog-agent-b7t5q                                         1/1       Running     0          12d
default       vizix-services-7bdccb48c4-2q8js                             1/1       Running     0          19m
default       vizix-tools-cpr88                                           0/1       Completed   0          12d
kube-system   etcd-kubctl-s-2vcpu-4gb-nyc3-01-master                      1/1       Running     0          27d
kube-system   kube-apiserver-kubctl-s-2vcpu-4gb-nyc3-01-master            1/1       Running     0          27d
kube-system   kube-controller-manager-kubctl-s-2vcpu-4gb-nyc3-01-master   1/1       Running     0          27d
kube-system   kube-dns-6f4fd4bdf-f7ssn                                    3/3       Running     0          27d
kube-system   kube-flannel-ds-dm5w4                                       1/1       Running     0          27d
kube-system   kube-flannel-ds-ns58w                                       1/1       Running     0          27d
kube-system   kube-flannel-ds-prnvf                                       1/1       Running     1          27d
kube-system   kube-flannel-ds-xck8p                                       1/1       Running     0          27d
kube-system   kube-proxy-2xrhl                                            1/1       Running     0          27d
kube-system   kube-proxy-lnt9r                                            1/1       Running     0          27d
kube-system   kube-proxy-m74ms                                            1/1       Running     0          27d
kube-system   kube-proxy-vqdxt                                            1/1       Running     0          27d
kube-system   kube-scheduler-kubctl-s-2vcpu-4gb-nyc3-01-master            1/1       Running     0          27d
kube-system   kubernetes-dashboard-5bd6f767c7-7qp75                       1/1       Running     0          26d

需要连接Kafka的POD使用PING或者Telnet就可以到达集群:

# kubectl exec -it vizix-services-7bdccb48c4-2q8js bash
bash-4.2# ping 10.132.123.177
PING 10.132.123.177 (10.132.123.177) 56(84) bytes of data.
64 bytes from 10.132.123.177: icmp_seq=1 ttl=63 time=0.540 ms
64 bytes from 10.132.123.177: icmp_seq=2 ttl=63 time=0.518 ms
64 bytes from 10.132.123.177: icmp_seq=3 ttl=63 time=0.432 ms
64 bytes from 10.132.123.177: icmp_seq=4 ttl=63 time=0.527 ms
^C
--- 10.132.123.177 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3000ms
rtt min/avg/max/mdev = 0.432/0.504/0.540/0.045 ms
bash-4.2# telnet 10.132.123.177 9092
Trying 10.132.123.177...
Connected to 10.132.123.177.
Escape character is '^]'.
^CConnection closed by foreign host.
bash-4.2#

但是 JAVA 应用程序不能。只用 docker 可以正常连接，但是 Kubernetes 启动 pod 时就不能了。

2018-05-30 01:25:06,993+0000 WARN  [localhost-startStop-1] com.tierconnect.riot.commons.services.broker.KafkaPublisher:: - 
Check if exists a connection to kafka server 10.132.123.177:9092 and services is able to publish to kafka. 

Kubernetes 有没有什么东西可以阻止某些特定的应用程序协议(protocol)从一个节点连接到外部主机？

这是服务的部署 YAML 文件:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: microservice1
  labels:
    app: services
spec:
  replicas: 1
  selector:
    matchLabels:
      app: services
  template:
    metadata:
      labels:
        app: services
    spec:
      containers:
      - name: microservice1
        image: random/java-image:v6.5.2
        env:
      - name: KAFKA_SERVERS
        value: "10.132.123.177:9092"

Answer 1

我使用端点和服务解决了这个问题。这样连接由 Kubernetes 管理:

    ---
    kind: "Service"
    apiVersion: "v1"
    metadata:
      name: "kafka"
    spec:
      ports:
        -
          name: "kafka"
          protocol: "TCP"
          port: 9092
          targetPort: 9092
          nodePort: 0
    ---
    kind: "Endpoints"
    apiVersion: "v1"
    metadata:
      name: "kafka"
    subsets:
      -
        addresses:
          -
            ip: "10.128.0.2"
        ports:
          -
            port: 9092
            name: "kafka"