如何在没有转发规则的情况下将kubernetes pod连接到外部世界(谷歌容器引擎)

Question

我正在使用谷歌的容器引擎服务,并获得一个运行服务器的pod在端口3000上侦听.我设置了服务以将端口80连接到该容器的端口3000.我能够使用其本地和公共IP来卷曲服务在节点内,但不是从外部.我设置了防火墙规则以允许端口80并将其发送到节点,但我不断从网络外部获得"连接被拒绝".我试图在没有转发规则的情况下这样做,因为只有一个pod,看起来转发规则需要花钱并进行负载平衡.我认为防火墙规则有效,因为当我添加createExternalLoadBalancer: true到服务的规范时,转发规则创建的外部IP按预期工作.我还需要做点什么吗？设置路线或什么？

controller.yaml

kind: ReplicationController
apiVersion: v1beta3
metadata:
    name: app-frontend
    labels:
        name: app-frontend
        app: app
        role: frontend
spec:
    replicas: 1
    selector:
        name: app-frontend
    template:
        metadata:
            labels:
                name: app-frontend
                app: app
                role: frontend
        spec:
            containers:
                - name: node-frontend
                  image: gcr.io/project_id/app-frontend
                  ports:
                    - name: app-frontend-port
                      containerPort: 3000
                      targetPort: 3000
                      protocol: TCP

service.yaml

kind: Service
apiVersion: v1beta3
metadata:
  name: app-frontend-service
  labels:
    name: app-frontend-service
    app: app
    role: frontend
spec:
  ports:
    - port: 80
      targetPort: app-frontend-port
      protocol: TCP
  publicIPs:
   - 123.45.67.89
  selector:
    name: app-frontend

---

编辑(其他详细信息): 创建此服务会添加这些在运行时找到的附加规则iptables -L -t nat

Chain KUBE-PORTALS-CONTAINER (1 references)
target     prot opt source               destination         
REDIRECT   tcp  --  anywhere             10.247.247.206       /* default/app-frontend-service: */ tcp dpt:http redir ports 56859
REDIRECT   tcp  --  anywhere             89.67.45.123.bc.googleusercontent.com  /* default/app-frontend-service: */ tcp dpt:http redir ports 56859
Chain KUBE-PORTALS-HOST (1 references)
target     prot opt source               destination         
DNAT       tcp  --  anywhere             10.247.247.206       /* default/app-frontend-service: */ tcp dpt:http to:10.241.69.28:56859
DNAT       tcp  --  anywhere             89.67.45.123.bc.googleusercontent.com  /* default/app-frontend-service: */ tcp dpt:http to:10.241.69.28:56859

我不完全了解iptables,所以我不确定目标端口如何匹配我的服务.我发现DNS的89.67.45.123.bc.googleusercontent.com解析为123.45.67.89.

kubectl get services显示我指定的IP地址和端口:

NAME                             IP(S)               PORT(S)
app-frontend-service             10.247.243.151      80/TCP
                                 123.45.67.89

在/var/log/kube-proxy.log中没有显示外部IP的最新信息

Answer 1

TL; DR:使用节点的内部IP作为服务定义中的公共IP.

如果在kube-proxy上启用详细日志记录,您将看到它似乎正在创建适当的IP表规则:

I0602 04:07:32.046823   24360 roundrobin.go:98] LoadBalancerRR service "default/app-frontend-service:" did not exist, created
I0602 04:07:32.047153   24360 iptables.go:186] running iptables -A [KUBE-PORTALS-HOST -t nat -m comment --comment default/app-frontend-service: -p tcp -m tcp -d 10.119.244.130/32 --dport 80 -j DNAT --to-destination 10.240.121.42:36970]
I0602 04:07:32.048446   24360 proxier.go:606] Opened iptables from-host portal for service "default/app-frontend-service:" on TCP 10.119.244.130:80
I0602 04:07:32.049525   24360 iptables.go:186] running iptables -C [KUBE-PORTALS-CONTAINER -t nat -m comment --comment default/app-frontend-service: -p tcp -m tcp -d 23.251.156.36/32 --dport 80 -j REDIRECT --to-ports 36970]
I0602 04:07:32.050872   24360 iptables.go:186] running iptables -A [KUBE-PORTALS-CONTAINER -t nat -m comment --comment default/app-frontend-service: -p tcp -m tcp -d 23.251.156.36/32 --dport 80 -j REDIRECT --to-ports 36970]
I0602 04:07:32.052247   24360 proxier.go:595] Opened iptables from-containers portal for service "default/app-frontend-service:" on TCP 23.251.156.36:80
I0602 04:07:32.053222   24360 iptables.go:186] running iptables -C [KUBE-PORTALS-HOST -t nat -m comment --comment default/app-frontend-service: -p tcp -m tcp -d 23.251.156.36/32 --dport 80 -j DNAT --to-destination 10.240.121.42:36970]
I0602 04:07:32.054491   24360 iptables.go:186] running iptables -A [KUBE-PORTALS-HOST -t nat -m comment --comment default/app-frontend-service: -p tcp -m tcp -d 23.251.156.36/32 --dport 80 -j DNAT --to-destination 10.240.121.42:36970]
I0602 04:07:32.055848   24360 proxier.go:606] Opened iptables from-host portal for service "default/app-frontend-service:" on TCP 23.251.156.36:80

列出iptables条目使用-L -t显示公共IP转换为反向DNS名称,如下所示:

Chain KUBE-PORTALS-CONTAINER (1 references)
target     prot opt source               destination         
REDIRECT   tcp  --  anywhere             10.119.240.2         /* default/kubernetes: */ tcp dpt:https redir ports 50353
REDIRECT   tcp  --  anywhere             10.119.240.1         /* default/kubernetes-ro: */ tcp dpt:http redir ports 54605
REDIRECT   udp  --  anywhere             10.119.240.10        /* default/kube-dns:dns */ udp dpt:domain redir ports 37723
REDIRECT   tcp  --  anywhere             10.119.240.10        /* default/kube-dns:dns-tcp */ tcp dpt:domain redir ports 50126
REDIRECT   tcp  --  anywhere             10.119.244.130       /* default/app-frontend-service: */ tcp dpt:http redir ports 36970
REDIRECT   tcp  --  anywhere             36.156.251.23.bc.googleusercontent.com  /* default/app-frontend-service: */ tcp dpt:http redir ports 36970

但添加该-n选项会显示IP地址(默认情况下,-L会对IP地址执行反向查找,这就是您查看DNS名称的原因):

Chain KUBE-PORTALS-CONTAINER (1 references)
target     prot opt source               destination         
REDIRECT   tcp  --  0.0.0.0/0            10.119.240.2         /* default/kubernetes: */ tcp dpt:443 redir ports 50353
REDIRECT   tcp  --  0.0.0.0/0            10.119.240.1         /* default/kubernetes-ro: */ tcp dpt:80 redir ports 54605
REDIRECT   udp  --  0.0.0.0/0            10.119.240.10        /* default/kube-dns:dns */ udp dpt:53 redir ports 37723
REDIRECT   tcp  --  0.0.0.0/0            10.119.240.10        /* default/kube-dns:dns-tcp */ tcp dpt:53 redir ports 50126
REDIRECT   tcp  --  0.0.0.0/0            10.119.244.130       /* default/app-frontend-service: */ tcp dpt:80 redir ports 36970
REDIRECT   tcp  --  0.0.0.0/0            23.251.156.36        /* default/app-frontend-service: */ tcp dpt:80 redir ports 36970

此时,您可以使用内部和外部IP从群集中访问服务:

$ curl 10.119.244.130:80
app-frontend-5pl5s
$ curl 23.251.156.36:80
app-frontend-5pl5s

在不添加防火墙规则的情况下,尝试远程连接到公共IP超时.如果添加防火墙规则,则可以可靠地拒绝连接:

$ curl 23.251.156.36
curl: (7) Failed to connect to 23.251.156.36 port 80: Connection refused

如果启用一些iptables日志记录:

sudo iptables -t nat -I KUBE-PORTALS-CONTAINER -m tcp -p tcp --dport 
80 -j LOG --log-prefix "WTF: "

然后grep输出,dmesg因为WTF它清楚地表明数据包到达VM的IP地址,而不是在服务上设置为公共IP的短暂外部IP地址.

事实证明,问题在于GCE有两种类型的外部IP:ForwardingRules(在DSTIP完整的情况下转发)和1对1 NAT(实际上将DSTIP重写为内部IP).VM的外部IP是后一种类型,因此当节点收到数据包时,IP表规则不匹配.

修复实际上非常简单(但不直观):使用节点的内部IP作为服务定义中的公共IP.更新service.yaml文件以将publicIP设置为内部IP(例如10.240.121.42)后,您将能够从GCE网络外部访问您的应用程序.