Downward API

概述

  Downward API 可以给在 Pod 中运行的进程暴露 Pod 的元数据。目前我们可以给容器传递以下数据:

• pod 的名称
• pod 的 IP
• pod 所在的命名空间
• pod 运行节点的名称
• pod 运行所归属的服务帐户的名称
• 每个容器请求的 CPU 和内存的使用量
• 每个容器可以使用的 CPU 和内存的限制
• pod 的标签
• pod 的注解

配置容器

通过环境变量向容器传递配置

  在 Pod 声明时，可以通过以下方式手动添加环境变量。Pod 通过读取环境变量即可完成读取容器信息的目标。

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
      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
      valueFrom:
        resourceFieldRef:
          resource: requests.cpu
          divisor: 1m
    - name: CONTAINER_MEMORY_LIMIT_KIBIBYTES
      valueFrom:
        resourceFieldRef:
          resource: limits.memory
          divisor: 1Ki

# 获取环境变量
$ 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_I=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
...

通过 downwardAPI 卷来传递元数据

  也可以通过定义 downwardAPI 卷并挂载到容器中。

apiVersion: v1
kind: Pod
metadata:
  name: downward
  labels:
    foo: bar
  annotations:
    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:
    - name: downward
      mountPath: /etc/downward
  volumes:
  - name: downward
    downwardAPI:
      items:
      - path: "podName"
        fieldRef:
          fieldPath: metadata.name
      - path: "podNamespace"
        fieldRef:
          fieldPath: metadata.namespace
      - path: "labels"
        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: limit.memory
          divisor: 1

  

# 查看 downwordAPI 卷中的文件
$ kubectl exec downward ls -l /etc/downward
-rw-r--r--   1 root    root  132  May 
-rw-r--r--
-rw-r--r--
-rw-r--r--
-rw-r--r--
-rw-r--r--