需求背景：一些自研插件通过sidecar容器提供服务，容器需要获取到当前所在节点的IP与hostname作为环境变量传递给应用。
Kubernetes通过环境变量可满足该需求。通过环境变量获取的内容如下：
status.podIP - POD的IPspec.serviceAccountName - Pod 服务帐号名称, 版本要求 v1.4.0-alpha.3spec.nodeName - 节点名称, 版本要求 v1.4.0-alpha.3status.hostIP - 节点 IP, 版本要求 v1.7.0-alpha.1
此外，Kubernetes通过downward API卷可以给容器提供POD信息、以及容器限额信息，详细可参考官网- Downward API 的能力
实践 - 向容器中注入主机IP与主机Hostname
deploy.yaml
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
| kind: Deployment
apiVersion: apps/v1
metadata:
name: nginx-deploy
spec:
replicas: 1
selector:
matchLabels:
app: my-nginx
template:
metadata:
labels:
app: my-nginx
spec:
containers:
- env:
- name: my_env
value: 'beta'
- name: MY_NODE_IP
valueFrom:
fieldRef: #通过fieldRef引入到env中
fieldPath: status.hostIP #注入hostIP信息
name: container-1
image: 'kweecr03.xxx.xxx.xxx:80/public/nginx:x86-1.20.1'
resources:
limits:
cpu: 500m
memory: 200Mi
requests:
cpu: 500m
memory: 200Mi
|
测试：
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
| $ kubectl apply -f deploy.yaml
deployment.apps/nginx-deploy created
$ kubectl get deploy
NAME READY UP-TO-DATE AVAILABLE AGE
nginx-deploy 1/1 1 1 6s
laomei@myworkspace:~/kubernetes/exec/exec15$ kubectl get po
NAME READY STATUS RESTARTS AGE
nginx-deploy-dfdf4f84d-v9w8r 1/1 Running 0 10s
$ kubectl exec -it nginx-deploy-dfdf4f84d-v9w8r env |grep my_env #查看容器的环境变量my_env
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
my_env=beta
$ kubectl exec -it nginx-deploy-dfdf4f84d-v9w8r env |grep MY_NODE_IP #查看容器的环境变量MY_NODE_IP
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
MY_NODE_IP=10.247.154.19
$ kubectl exec -it nginx-deploy-dfdf4f84d-v9w8r env |grep MY_NODE_NAME #查看容器的环境变量MY_NODE_NAME
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
MY_NODE_NAME=10.247.154.19
|
从这里可以看出其实其节点名和节点IP是一致的，之所以这样是因为K8s安装时节点命名直接引用了IP地址，如下：
1
2
3
4
| $ kubectl get nodes
NAME STATUS ROLES AGE VERSION
10.247.154.19 Ready <none> 23d v1.19.10-r0-CCE21.11.1.B006-21.11.1.B006
10.247.154.61 Ready <none> 23d v1.19.10-r0-CCE21.11.1.B006-21.11.1.B006
|
但是节点本身在/etc/hostname中配置的名字是对的，那如何将这个配置文件传递给容器呢？
实践2 - 通过hostpath卷引入容器中
接上面的实践1，我们可以通过hostpath将主机的/etc/hostname作为volume挂载到容器中的某个目录，容器如果需要读取，在应用中读取该volume即可。
deploy.yaml
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
| kind: Deployment
apiVersion: apps/v1
metadata:
name: nginx-deploy
spec:
replicas: 1
selector:
matchLabels:
app: my-nginx
template:
metadata:
labels:
app: my-nginx
spec:
containers:
- env:
- name: my_env
value: 'beta'
- name: MY_NODE_IP
valueFrom:
fieldRef:
fieldPath: status.hostIP
- name: MY_NODE_NAME
valueFrom:
fieldRef:
fieldPath: spec.nodeName
name: container-1
image: 'kweecr03.xxx.xxx.xxx:80/public/nginx:x86-1.20.1'
resources:
limits: # limits与requests建议取值保持一致，避免扩缩容过程中出现震荡
cpu: 500m
memory: 200Mi
requests:
cpu: 500m
memory: 200Mi
volumeMounts:
- mountPath: /etc/hostname_eks
name: hostname #引入下面的名字
volumes:
- hostPath:
path: /etc/hostname #主机目录
name: hostname #命名为hostame
|
部署后查询：
1
2
3
| $ kubectl exec -it nginx-deploy-6677765846-bbrh5 cat /etc/hostname_eks
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
kweekshcgp-nsdk4
|
其本质是引入hostpath文件，但最终是要被容器中的应用调用的。
