Kubernetes K8S之Pod跨namespace名称空间访问Service服务

时间:2023-09-04 15:13:49

Kubernetes的两个Service(ServiceA、ServiceB)和对应的Pod(PodA、PodB)分别属于不同的namespace名称空间,现需要PodA和PodB跨namespace名称空间并通过Service实现互访。应该如何实现?

场景需求

Kubernetes的两个Service(ServiceA、ServiceB)和对应的Pod(PodA、PodB)分别属于不同的namespace名称空间,现需要PodA和PodB跨namespace名称空间并通过Service实现互访。如何实现?

说明:这里是指通过Service的Name进行通信访问,而不是通过Service的IP【因因为每次重启Service,NAME不会改变,而IP是会改变的】。

主机配置规划

服务器名称(hostname) 系统版本 配置 内网IP 外网IP(模拟)
k8s-master CentOS7.7 2C/4G/20G 172.16.1.110 10.0.0.110
k8s-node01 CentOS7.7 2C/4G/20G 172.16.1.111 10.0.0.111
k8s-node02 CentOS7.7 2C/4G/20G 172.16.1.112 10.0.0.112

创建Service和Pod

相关yaml文件

 [root@k8s-master cross_ns]# pwd
/root/k8s_practice/cross_ns
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# cat deply_service_myns.yaml
apiVersion: v1
kind: Namespace
metadata:
name: myns
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: myapp-deploy1
namespace: myns
spec:
replicas:
selector:
matchLabels:
app: myapp
release: v1
template:
metadata:
labels:
app: myapp
release: v1
spec:
containers:
- name: myapp
image: registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort:
---
apiVersion: v1
kind: Service
metadata:
name: myapp-clusterip1
namespace: myns
spec:
type: ClusterIP # 默认类型
selector:
app: myapp
release: v1
ports:
- name: http
port:
targetPort: [root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# cat deply_service_mytest.yaml
apiVersion: v1
kind: Namespace
metadata:
name: mytest
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: myapp-deploy2
namespace: mytest
spec:
replicas:
selector:
matchLabels:
app: myapp
release: v2
template:
metadata:
labels:
app: myapp
release: v2
spec:
containers:
- name: myapp
image: registry.cn-beijing.aliyuncs.com/google_registry/myapp:v2
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort:
---
apiVersion: v1
kind: Service
metadata:
name: myapp-clusterip2
namespace: mytest
spec:
type: ClusterIP # 默认类型
selector:
app: myapp
release: v2
ports:
- name: http
port:
targetPort:

运行yaml文件

 kubectl apply -f deply_service_myns.yaml
kubectl apply -f deply_service_mytest.yaml

查看myns名称空间信息

 [root@k8s-master cross_ns]# kubectl get svc -n myns -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
myapp-clusterip1 ClusterIP 10.100.61.11 <none> /TCP 3m app=myapp,release=v1
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get deploy -n myns -o wide
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
myapp-deploy1 / 3m7s myapp registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp,release=v1
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get rs -n myns -o wide
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
myapp-deploy1-5b9d78576c 3m15s myapp registry.cn-beijing.aliyuncs.com/google_registry/myapp:v1 app=myapp,pod-template-hash=5b9d78576c,release=v1
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get pod -n myns -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
myapp-deploy1-5b9d78576c-wfw4n / Running 3m20s 10.244.2.136 k8s-node02 <none> <none>
myapp-deploy1-5b9d78576c-zsfjl / Running 3m20s 10.244.3.193 k8s-node01 <none> <none>

查看mytest名称空间信息

 [root@k8s-master cross_ns]# kubectl get svc -n mytest -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
myapp-clusterip2 ClusterIP 10.100.201.103 <none> /TCP 4m9s app=myapp,release=v2
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get deploy -n mytest -o wide
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
myapp-deploy2 / 4m15s myapp registry.cn-beijing.aliyuncs.com/google_registry/myapp:v2 app=myapp,release=v2
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get rs -n mytest -o wide
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
myapp-deploy2-dc8f96497 4m22s myapp registry.cn-beijing.aliyuncs.com/google_registry/myapp:v2 app=myapp,pod-template-hash=dc8f96497,release=v2
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get pod -n mytest -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
myapp-deploy2-dc8f96497-nnkqn / Running 4m27s 10.244.3.194 k8s-node01 <none> <none>
myapp-deploy2-dc8f96497-w47dt / Running 4m27s 10.244.2.137 k8s-node02 <none> <none>

只看Service和Pod

 [root@k8s-master cross_ns]# kubectl get pod -A -o wide | grep -E '(my)|(NAME)'
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
myns myapp-deploy1-5b9d78576c-wfw4n / Running 41m 10.244.2.136 k8s-node02 <none> <none>
myns myapp-deploy1-5b9d78576c-zsfjl / Running 41m 10.244.3.193 k8s-node01 <none> <none>
mytest myapp-deploy2-dc8f96497-nnkqn / Running 41m 10.244.3.194 k8s-node01 <none> <none>
mytest myapp-deploy2-dc8f96497-w47dt / Running 41m 10.244.2.137 k8s-node02 <none> <none>
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get svc -A -o wide | grep -E '(my)|(NAME)'
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
myns myapp-clusterip1 ClusterIP 10.100.61.11 <none> /TCP 41m app=myapp,release=v1
mytest myapp-clusterip2 ClusterIP 10.100.201.103 <none> /TCP 41m app=myapp,release=v2

pod跨名称空间namespace与Service通信

说明:是通过Service的NAME进行通信,而不是Service的IP【因为每次重启Service,NAME不会改变,而IP是会改变的】。

 # 进入ns名称空间下的一个Pod容器
[root@k8s-master cross_ns]# kubectl exec -it -n myns myapp-deploy1-5b9d78576c-wfw4n sh
/ # cd /root/
### 如下说明在同一名称空间下,通信无问题
~ # ping myapp-clusterip1
PING myapp-clusterip1 (10.100.61.11): data bytes
bytes from 10.100.61.11: seq= ttl= time=0.046 ms
bytes from 10.100.61.11: seq= ttl= time=0.081 ms
~ #
~ # wget myapp-clusterip1 -O myns.html
Connecting to myapp-clusterip1 (10.100.61.11:)
myns.html %
~ #
~ # cat myns.html
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a> ### 如下说明在不同的名称空间下,通过Service的NAME进行通信存在问题
~ # ping myapp-clusterip2
ping: bad address 'myapp-clusterip2'
~ #
~ # wget myapp-clusterip2 -O mytest.html
wget: bad address 'myapp-clusterip2'

实现跨namespace与Service通信

通过Service的ExternalName类型即可实现跨namespace名称空间与Service通信。

Service域名格式:$(service name).$(namespace).svc.cluster.local,其中 cluster.local 为指定的集群的域名

相关yaml文件

 [root@k8s-master cross_ns]# pwd
/root/k8s_practice/cross_ns
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# cat svc_ExternalName_visit.yaml
# 实现 myns 名称空间的pod,访问 mytest 名称空间的Service:myapp-clusterip2
apiVersion: v1
kind: Service
metadata:
name: myapp-clusterip1-externalname
namespace: myns
spec:
type: ExternalName
externalName: myapp-clusterip2.mytest.svc.cluster.local
ports:
- name: http
port:
targetPort:
---
# 实现 mytest 名称空间的Pod,访问 myns 名称空间的Service:myapp-clusterip1
apiVersion: v1
kind: Service
metadata:
name: myapp-clusterip2-externalname
namespace: mytest
spec:
type: ExternalName
externalName: myapp-clusterip1.myns.svc.cluster.local
ports:
- name: http
port:
targetPort:

运行yaml文件

 [root@k8s-master cross_ns]# kubectl apply -f svc_ExternalName_visit.yaml
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get svc -A -o wide | grep -E '(ExternalName)|(NAME)'
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
myns myapp-clusterip1-externalname ExternalName <none> myapp-clusterip2.mytest.svc.cluster.local /TCP 28s <none>
mytest myapp-clusterip2-externalname ExternalName <none> myapp-clusterip1.myns.svc.cluster.local /TCP 28s <none>

pod跨名称空间namespace与Service通信

到目前所有service和pod信息查看

 [root@k8s-master cross_ns]# kubectl get svc -A -o wide | grep -E '(my)|(NAME)'
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
myns myapp-clusterip1 ClusterIP 10.100.61.11 <none> /TCP 62m app=myapp,release=v1
myns myapp-clusterip1-externalname ExternalName <none> myapp-clusterip2.mytest.svc.cluster.local /TCP 84s <none>
mytest myapp-clusterip2 ClusterIP 10.100.201.103 <none> /TCP 62m app=myapp,release=v2
mytest myapp-clusterip2-externalname ExternalName <none> myapp-clusterip1.myns.svc.cluster.local /TCP 84s <none>
[root@k8s-master cross_ns]#
[root@k8s-master cross_ns]# kubectl get pod -A -o wide | grep -E '(my)|(NAME)'
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
myns myapp-deploy1-5b9d78576c-wfw4n / Running 62m 10.244.2.136 k8s-node02 <none> <none>
myns myapp-deploy1-5b9d78576c-zsfjl / Running 62m 10.244.3.193 k8s-node01 <none> <none>
mytest myapp-deploy2-dc8f96497-nnkqn / Running 62m 10.244.3.194 k8s-node01 <none> <none>
mytest myapp-deploy2-dc8f96497-w47dt / Running 62m 10.244.2.137 k8s-node02 <none> <none>

myns 名称空间的pod,访问 mytest 名称空间的Service:myapp-clusterip2

 [root@k8s-master cross_ns]# kubectl exec -it -n myns myapp-deploy1-5b9d78576c-wfw4n sh
/ # cd /root/
### 如下说明在同一名称空间下,通信无问题
~ # ping myapp-clusterip1
PING myapp-clusterip1 (10.100.61.11): data bytes
bytes from 10.100.61.11: seq= ttl= time=0.057 ms
bytes from 10.100.61.11: seq= ttl= time=0.071 ms
………………
~ #
~ # wget myapp-clusterip1 -O myns.html
Connecting to myapp-clusterip1 (10.100.61.11:)
myns.html %
~ #
~ # cat myns.html
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a> ### 如下说明通过Service externalname类型,实现了Pod跨namespace名称空间与Service访问
~ # ping myapp-clusterip1-externalname
PING myapp-clusterip1-externalname (10.100.201.103): data bytes
bytes from 10.100.201.103: seq= ttl= time=0.050 ms
bytes from 10.100.201.103: seq= ttl= time=0.311 ms
………………
~ #
~ # wget myapp-clusterip1-externalname -O mytest.html
Connecting to myapp-clusterip1-externalname (10.100.201.103:)
mytest.html %
~ #
~ # cat mytest.html
Hello MyApp | Version: v2 | <a href="hostname.html">Pod Name</a>

mytest 名称空间的Pod,访问 myns 名称空间的Service:myapp-clusterip1

 [root@k8s-master cross_ns]# kubectl exec -it -n mytest myapp-deploy2-dc8f96497-w47dt sh
/ # cd /root/
### 如下说明在同一名称空间下,通信无问题
~ # ping myapp-clusterip2
PING myapp-clusterip2 (10.100.201.103): data bytes
bytes from 10.100.201.103: seq= ttl= time=0.087 ms
bytes from 10.100.201.103: seq= ttl= time=0.073 ms
………………
~ #
~ # wget myapp-clusterip2 -O mytest.html
Connecting to myapp-clusterip2 (10.100.201.103:)
mytest.html %
~ #
~ # cat mytest.html
Hello MyApp | Version: v2 | <a href="hostname.html">Pod Name</a> ### 如下说明通过Service externalname类型,实现了Pod跨namespace名称空间与Service访问
~ # ping myapp-clusterip2-externalname
PING myapp-clusterip2-externalname (10.100.61.11): data bytes
bytes from 10.100.61.11: seq= ttl= time=0.089 ms
bytes from 10.100.61.11: seq= ttl= time=0.071 ms
………………
~ #
~ # wget myapp-clusterip2-externalname -O myns.html
Connecting to myapp-clusterip2-externalname (10.100.61.11:)
myns.html %
~ #
~ # cat myns.html
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>

由上可见,实现了Pod跨namespace名称空间与Service访问。

完毕!


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Kubernetes K8S之Pod跨namespace名称空间访问Service服务