Pod使用DownwardAPIVolumeFile将有关其自身的信息公开给Pod中运行的Container。DownwardAPIVolumeFile可以公开Pod字段和Container字段。

@[TOC]

有两种方法可以将Pod和Container字段公开给正在运行的Container:

  1. 环境变量
  2. DownwardAPIVolumeFiles

环境变量的方式

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apiVersion: v1
kind: Pod
metadata:
name: dapi-envars-fieldref
spec:
containers:
- name: test-container
image: k8s.gcr.io/busybox
command: [ "sh", "-c"]
args:
- while true; do
echo -en '\n';
printenv MY_NODE_NAME MY_POD_NAME MY_POD_NAMESPACE;
printenv MY_POD_IP MY_POD_SERVICE_ACCOUNT;
sleep 10;
done;
env:
- name: MY_NODE_NAME
valueFrom:
fieldRef:
fieldPath: spec.nodeName
- name: MY_POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: MY_POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
- name: MY_POD_IP
valueFrom:
fieldRef:
fieldPath: status.podIP
- name: MY_POD_SERVICE_ACCOUNT
valueFrom:
fieldRef:
fieldPath: spec.serviceAccountName
restartPolicy: Never

使用DownwardAPIVolumeFiles

存储Pod字段

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apiVersion: v1
kind: Pod
metadata:
name: kubernetes-downwardapi-volume-example
labels:
zone: us-est-coast
cluster: test-cluster1
rack: rack-22
annotations:
build: two
builder: john-doe
spec:
containers:
- name: client-container
image: k8s.gcr.io/busybox
command: ["sh", "-c"]
args:
- while true; do
if [[ -e /etc/podinfo/labels ]]; then
echo -en '\n\n'; cat /etc/podinfo/labels; fi;
if [[ -e /etc/podinfo/annotations ]]; then
echo -en '\n\n'; cat /etc/podinfo/annotations; fi;
sleep 5;
done;
volumeMounts:
- name: podinfo
mountPath: /etc/podinfo
readOnly: false
volumes:
- name: podinfo
downwardAPI:
items:
- path: "labels"
fieldRef:
fieldPath: metadata.labels
- path: "annotations"
fieldRef:
fieldPath: metadata.annotations

fieldRef支持的字段:

  • spec.nodeName - 节点的名称
  • status.hostIP - 节点的IP
  • metadata.name - pod的名字
  • metadata.namespace - pod的命名空间
  • status.podIP - pod的IP地址
  • spec.serviceAccountName - pod的服务帐户名称
  • metadata.uid - pod的UID
  • metadata.labels[‘‘] - pod标签的值(例如metadata.labels[‘mylabel’]); 可在Kubernetes 1.9+中找到
  • metadata.annotations[‘‘] - pod的注释的值(例如metadata.annotations[‘myannotation’]); 可在Kubernetes 1.9+中找到

  • metadata.labels - 所有pod的标签,格式为label-key=”escaped-label-value”每行一个label

  • metadata.annotations - 所有pod的注释,格式为annotation-key=”escaped-annotation-value”每行一个annotation

存储容器字段

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apiVersion: v1
kind: Pod
metadata:
name: kubernetes-downwardapi-volume-example-2
spec:
containers:
- name: client-container
image: k8s.gcr.io/busybox:1.24
command: ["sh", "-c"]
args:
- while true; do
echo -en '\n';
if [[ -e /etc/podinfo/cpu_limit ]]; then
echo -en '\n'; cat /etc/podinfo/cpu_limit; fi;
if [[ -e /etc/podinfo/cpu_request ]]; then
echo -en '\n'; cat /etc/podinfo/cpu_request; fi;
if [[ -e /etc/podinfo/mem_limit ]]; then
echo -en '\n'; cat /etc/podinfo/mem_limit; fi;
if [[ -e /etc/podinfo/mem_request ]]; then
echo -en '\n'; cat /etc/podinfo/mem_request; fi;
sleep 5;
done;
resources:
requests:
memory: "32Mi"
cpu: "125m"
limits:
memory: "64Mi"
cpu: "250m"
volumeMounts:
- name: podinfo
mountPath: /etc/podinfo
readOnly: false
volumes:
- name: podinfo
downwardAPI:
items:
- path: "cpu_limit"
resourceFieldRef:
containerName: client-container
resource: limits.cpu
divisor: 1m
- path: "cpu_request"
resourceFieldRef:
containerName: client-container
resource: requests.cpu
divisor: 1m
- path: "mem_limit"
resourceFieldRef:
containerName: client-container
resource: limits.memory
divisor: 1Mi
- path: "mem_request"
resourceFieldRef:
containerName: client-container
resource: requests.memory
divisor: 1Mi

resourceFieldRef 支持的字段:

  • Container的CPU限制:limits.cpu
  • Container的CPU请求:requests.cpu
  • Container的内存限制:limits.memory
  • Container的内存请求:requests.memory

projected 使用 downwardAPI

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apiVersion: v1
kind: Pod
metadata:
name: volume-test
spec:
containers:
- name: container-test
image: busybox
volumeMounts:
- name: all-in-one
mountPath: "/projected-volume"
readOnly: true
volumes:
- name: all-in-one
projected:
sources:
- secret:
name: mysecret
items:
- key: username
path: my-group/my-username
- downwardAPI:
items:
- path: "labels"
fieldRef:
fieldPath: metadata.labels
- path: "cpu_limit"
resourceFieldRef:
containerName: container-test
resource: limits.cpu
- configMap:
name: myconfigmap
items:
- key: config
path: my-group/my-config

.downwardAPI.fieldRef.fieldPath` 支持的类型:

  • “metadata.annotations”
  • “metadata.labels”
  • “metadata.name”
  • “metadata.namespace”
  • “metadata.uid”

参考

  1. https://kubernetes.io/docs/tasks/inject-data-application/downward-api-volume-expose-pod-information/
  2. https://kubernetes.io/docs/tasks/inject-data-application/environment-variable-expose-pod-information/
  3. https://kubernetes.io/docs/concepts/storage/volumes/#projected