Kubernetes通过downwardAPI传递元数据

代码8.1 在环境变量中使用downwardAPI: downward-api-env.yaml
apiVersion: v1
kind: Pod
metadata:
name: downward
spec:
containers:
- name: main
image: busybox
command: ["sleep", "9999999"]
resources:
requests:
cpu: 15m
memory: 100Ki
limits:
cpu: 100m
memory: 4Mi
env:
- name: POD_NAME #引用pod manifest中的元数据名称字段，而不是设定一个具体的值
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
- name: POD_IP
valueFrom:
fieldRef:
fieldPath: status.podIP
- name: NODE_NAME
valueFrom:
fieldRef:
fieldPath: spec.nodeName
- name: SERVICE_ACCOUNT
valueFrom:
fieldRef:
fieldPath: spec.serviceAccountName
- name: CONTAINER_CPU_REQUEST_MILLICORES #容器请求的CPU和内存使用量是引用resourceFieldRef字段，而不是fieldRef字段
valueFrom:
resourceFieldRef:
resource: requests.cpu
divisor: 1m #对于资源相关的字段，定义一个基数单位，从而生成每一部分的值
- name: CONTAINER_MEMORY_LIMIT_KIBIBYTES
valueFrom:
resourceFieldRef:
resource: limits.memory
divisor: 1Ki

代码 8.2 downward pod中的环境变量
$ kubectl exec downward env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=downward
CONTAINER_MEMORY_LIMIT_KIBIBYTES=4096
POD_NAME=downward
POD_NAMESPACE=default
POD_IP=10.0.0.10
NODE_NAME=gke-kubia-default-pool-32a2cac8-sgl7
SERVICE_ACCOUNT=default
CONTAINER_CPU_REQUEST_MILLICORES=15
KUBERNETES_SERVICE_HOST=10.3.240.1
KUBERNETES_SERVICE_PORT=443

#代码8.3 —个带有downwardAPi卷的pod示例:downward-api-volume.yaml
apiVersion: v1
kind: Pod
metadata:
name: downward
labels:
foo: bar
annotations: #通过downwardAPI卷来暴露这些标签和注解
key1: value1
key2: |
multi
line
value
spec:
containers:
- name: main
image: busybox
command: ["sleep", "9999999"]
resources:
requests:
cpu: 15m
memory: 100Ki
limits:
cpu: 100m
memory: 4Mi
volumeMounts: #在/etc/downward目录下挂载这个downward卷
- name: downward
mountPath: /etc/downward
volumes:
- name: downward #通过将卷名字设定为downward来定义一个downwardAPI卷
downwardAPI:
items:
- path: "podName" #pod的名称（来自manifest文件中的metadata.name字段）将被写入podName中
fieldRef:
fieldPath: metadata.name
- path: "podNamespace"
fieldRef:
fieldPath: metadata.namespace
- path: "labels" #pod的标签将被保存到/etc/downward/labels文件中
fieldRef:
fieldPath: metadata.labels
- path: "annotations"
fieldRef:
fieldPath: metadata.annotations
- path: "containerCpuRequestMilliCores"
resourceFieldRef:
containerName: main
resource: requests.cpu
divisor: 1m
- path: "containerMemoryLimitBytes"
resourceFieldRef:
containerName: main
resource: limits.memory
divisor: 1

#代码8.4 downwordAPI卷中的文件
$ kubectl exec downward ls -lL /etc/downward
-rw-r- -r-- 1 root root 134 May 25 10:23 annotations
-rw-r- -r-- 1 root root 2 May 25 10:23 containerCpuRequestMilliCores
-rw-r- -r-- 1 root root 7 May 25 10:23 containerMemoryLimitBytes
-rw-r- -r-- 1 root root 9 May 25 10:23 labels
-rw-r- -r-- 1 root root 8 May 25 10:23 podName
-rw-r- -r-- 1 root root 7 May 25 10:23 podNamespace

#代码8.5 展示 downwardAPI卷中的标签和注解
$ kubectl exec downward cat /etc/downward/labels
foo="bar"
$ kubectl exec downward cat /etc/downward/annotations
key1="value1"
key2="multi\nline\nvalue\n"
kubernetes.io/config.seen="2016-11-28T14:27:45.664924282Z"
kubernetes.io/config.source="api"

#代码8.6 在downwardAPI卷中引用容器级的元数据
spec:
volumes:
- name: downward
downwardAPI：
items：
- path： "containerCpuRequestMilliCores"
resourceFieldRef:
containerName: main #必须制定容器名称
resource:requests.cpu
divisor： 1m