What?

This is a docker container intended to run inside a kubernetes cluster to collect config maps with a specified label and store the included files in an local folder. It can also send an HTTP request to a specified URL after a configmap change. The main target is to be run as a sidecar container to supply an application with information from the cluster.

Why?

This is our simple way to provide files from configmaps or secrets to a service and keep them updated during runtime.

How?

Run the container created by this repo together with your application in a single pod with a shared volume. Specify which label should be monitored and where the files should be stored. By adding additional env variables the container can send an HTTP request to specified URL.

Where?

Images are available at:

• docker.io/kiwigrid/k8s-sidecar
• quay.io/kiwigrid/k8s-sidecar
• ghcr.io/kiwigrid/k8s-sidecar

All are identical multi-arch images built for amd64, arm64, arm/v7, ppc64le and s390x

Features

• Extract files from config maps and secrets
• Filter based on label
• Update/Delete on change of configmap or secret
• Enforce unique filenames
• CI tests for k8s v1.21-v1.27
• Support binaryData for both Secret and ConfigMap kinds
  • Binary data content is base64 decoded before generating the file on disk
  • Values can also be base64 encoded URLs that download binary data e.g. executables
    • The key in the ConfigMap/Secret must end with ".url" (see)

Usage

Example for a simple deployment can be found in example.yaml. Depending on the cluster setup you have to grant yourself admin rights first:

kubectl create clusterrolebinding cluster-admin-binding --clusterrole cluster-admin   --user $(gcloud config get-value account)

One can override the default directory that files are copied into using a configmap annotation defined by the environment variable FOLDER_ANNOTATION (if not present it will default to k8s-sidecar-target-directory). The sidecar will attempt to create directories defined by configmaps if they are not present. Example configmap annotation:

metadata:
  annotations:
    k8s-sidecar-target-directory: "/path/to/target/directory"

If the filename ends with .url suffix, the content will be processed as a URL which the target file contents will be downloaded from.

Configuration Environment Variables