How to get Pod information Downward API in container in kubernetes

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One: preface

In some clusters, each node in the cluster needs to write its own ID and process-bound IP and other information into the configuration file in advance, read the information when the process starts, and then publish it to some place similar to the service registry, so as to realize the automatic discovery of cluster nodes.

Downward API can be used at this time, the specific approach is to write a pre-start script or Init Container, through the environment variables or files to obtain the Pod's own name, IP address and other information, and then write it into the configuration file of the main program, and finally start the main program.

Second: the way of realization

Downward API can inject Pod information into the container in two ways.

1. Environment variables: for a single variable, you can inject Pod information and Container information into the container.

2.Volume mount: generates a file of array class information and mounts it inside the container.

Three: examples

Environment variable mode, injecting Pod information into environment variable dapi-test-pod.yaml

ApiVersion: v1

Kind: Pod

Metadata:

Name: dapi-test-pod

Namespace: default

Spec:

Containers:

-name: test-container

Image: busybox

Command: ["/ bin/sh", "- c", "env"]

Env:

-name: MY_POD_NAME

ValueFrom:

FieldRef:

FieldPath: metadata.name

-name: MY_POD_NAMESPACE

ValueFrom:

FieldRef:

FieldPath: metadata.namespace

-name: MY_POD_NAMES

ValueFrom:

FieldRef:

FieldPath: status.podIP

Kubectl create-f dapi-test-pod.yaml

Kubectl logs dapi-test-pod

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