bumbacea/k8s-sidecar repository overview

⁠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. This was inspired by kiwigrid/k8s-sidecar⁠ and is aiming to be a golang port of that app. It started when I considered usage of 100MB of ram too much for the declared scope.

⁠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/bumbacea/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
• 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

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