我正在尝试将单个数据库实例公开为两个 Kubernetes 命名空间中的服务。 Kubernetes 版本 1.11.3 在 Ubuntu 16.04.1 上运行。数据库服务是可见的并且在默认命名空间中工作。我在非默认命名空间中创建了一个ExternalName 服务,引用默认命名空间中的完全限定域名,如下所示:
kind: Service
apiVersion: v1
metadata:
name: ws-mysql
namespace: wittlesouth
spec:
type: ExternalName
externalName: mysql.default.svc.cluster.local
ports:
- port: 3306
服务正在运行:
eric$ kubectl describe service ws-mysql --namespace=wittlesouth
Name: ws-mysql
Namespace: wittlesouth
Labels: <none>
Annotations: <none>
Selector: <none>
Type: ExternalName
IP:
External Name: mysql.default.svc.cluster.local
Port: <unset> 3306/TCP
TargetPort: 3306/TCP
Endpoints: <none>
Session Affinity: None
Events: <none>
如果我检查是否可以通过在 wittlesouth 命名空间中运行的 pod 中通过名称找到该服务,则该服务名称不会解析,但该命名空间中的其他服务(即 Jira)会解析:
root@rs-ws-diags-8mgqq:/# nslookup mysql.default.svc.cluster.local
Server: 10.96.0.10
Address: 10.96.0.10#53
Name: mysql.default.svc.cluster.local
Address: 10.99.120.208
root@rs-ws-diags-8mgqq:/# nslookup ws-mysql.wittlesouth
Server: 10.96.0.10
Address: 10.96.0.10#53
*** Can't find ws-mysql.wittlesouth: No answer
root@rs-ws-diags-8mgqq:/# nslookup ws-mysql
Server: 10.96.0.10
Address: 10.96.0.10#53
*** Can't find ws-mysql: No answer
root@rs-ws-diags-8mgqq:/# nslookup ws-mysql.wittlesouth
Server: 10.96.0.10
Address: 10.96.0.10#53
*** Can't find ws-mysql.wittlesouth: No answer
root@rs-ws-diags-8mgqq:/# nslookup ws-mysql.wittlesouth.svc.cluster.local
Server: 10.96.0.10
Address: 10.96.0.10#53
*** Can't find ws-mysql.wittlesouth.svc.cluster.local: No answer
root@rs-ws-diags-8mgqq:/# nslookup ws-mysql.wittlesouth
Server: 10.96.0.10
Address: 10.96.0.10#53
*** Can't find ws-mysql.wittlesouth: No answer
root@rs-ws-diags-8mgqq:/# nslookup jira.wittlesouth
Server: 10.96.0.10
Address: 10.96.0.10#53
Name: jira.wittlesouth.svc.cluster.local
Address: 10.105.30.239
对这里可能出现的问题有什么想法吗?目前,我已经通过更新需要使用数据库来引用在默认命名空间中运行的服务的完全限定域名的应用程序来解决这个问题,但我宁愿避免这种情况。我的最终目的是让命名空间拥有单独的数据库实例,并且希望在实际建立第二个实例之前部署配置为以这种方式工作的应用程序。
对于带有 coredns 和 calico 的 Kubernetes 1.11.2,这对我不起作用。仅当您直接在外部服务运行的命名空间中引用外部服务时,它才有效:
$ kubectl get pods -n default
NAME READY STATUS RESTARTS AGE
mysql-0 2/2 Running 0 17m
mysql-1 2/2 Running 0 16m
$ kubectl get pods -n wittlesouth
NAME READY STATUS RESTARTS AGE
ricos-dummy-pod 1/1 Running 0 14s
kubectl exec -it ricos-dummy-pod -n wittlesouth bash
root@ricos-dummy-pod:/# ping mysql.default.svc.cluster.local
PING mysql.default.svc.cluster.local (192.168.1.40): 56 data bytes
64 bytes from 192.168.1.40: icmp_seq=0 ttl=62 time=0.578 ms
64 bytes from 192.168.1.40: icmp_seq=1 ttl=62 time=0.632 ms
64 bytes from 192.168.1.40: icmp_seq=2 ttl=62 time=0.628 ms
^C--- mysql.default.svc.cluster.local ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.578/0.613/0.632/0.025 ms
root@ricos-dummy-pod:/# ping ws-mysql
ping: unknown host
root@ricos-dummy-pod:/# exit
$ kubectl get svc mysql
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
mysql ClusterIP None <none> 3306/TCP 45d
$ kubectl describe svc mysql
Name: mysql
Namespace: default
Labels: app=mysql
Annotations: <none>
Selector: app=mysql
Type: ClusterIP
IP: None
Port: mysql 3306/TCP
TargetPort: 3306/TCP
Endpoints: 192.168.1.40:3306,192.168.2.25:3306
Session Affinity: None
Events: <none>
仅根据 kube-dns 支持ExternalName服务功能docs https://coredns.io/plugins/kubernetes/Kubernetes 1.11.x 默认为 coredns。您可能想尝试从 coredns 更改为 kube-dns 或者可能更改configs https://coredns.io/plugins/kubernetes/用于您的 coredns 部署。我希望在某个时候可以使用 coredns 来实现这一点。
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