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 a html 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. The contained python script is working with the Kubernetes API 1.10

Why?

Currently (April 2018) there is no simple way to hand files in configmaps to a service and keep them updated during runtime.

How?

Run the container created by this repo together you application in an 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 a html request to specified URL.

Features

• Extract files from config maps
• Filter based on label
• Update/Delete on change of configmap

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

If the filename ends with .url suffix, the content will be processed as an URL the target file will be downloaded and used as the content file.

Configuration Environment Variables

• LABEL

  • description: Label that should be used for filtering
  • required: true
  • type: string

• FOLDER

  • description: Folder where the files should be placed
  • required: true
  • type: string

• FOLDER_ANNOTATION

  • description: The annotation the sidecar will look for in configmaps to override the destination folder for files, defaults to "k8s-sidecar-target-directory"
  • required: false
  • type: string

• NAMESPACE

  • description: If specified, the sidecar will search for config-maps inside this namespace. Otherwise the namespace in which the sidecar is running will be used. It's also possible to specify ALL to search in all namespaces.
  • required: false
  • type: string

• RESOURCE

  • description: Resouce type, which is monitored by the sidecar. Options: configmap (default), secret, both
  • required: false
  • default: configmap
  • type: string

• METHOD

  • description: If METHOD is set with LIST, the sidecar will just list config-maps and exit. Default is watch.
  • required: false
  • type: string

• REQ_URL

  • description: URL to which send a request after a configmap got reloaded
  • required: false
  • type: URI

• REQ_METHOD

  • description: Request method GET(default) or POST
  • required: false
  • type: string

• REQ_PAYLOAD

  • description: If you use POST you can also provide json payload
  • required: false
  • type: json

• REQ_RETRY_TOTAL

  • description: Total number of retries to allow
  • required: false
  • default: 5
  • type: integer

• REQ_RETRY_CONNECT

  • description: How many connection-related errors to retry on
  • required: false
  • default: 5
  • type: integer

• REQ_RETRY_READ

  • description: How many times to retry on read errors
  • required: false
  • default: 5
  • type: integer

• REQ_RETRY_BACKOFF_FACTOR

  • description: A backoff factor to apply between attempts after the second try
  • required: false
  • default: 0.2
  • type: float

• REQ_TIMEOUT

  • description: many seconds to wait for the server to send data before giving up
  • required: false
  • default: 10
  • type: float

• SKIP_TLS_VERIFY

  • description: Set to true to skip tls verification for kube api calls
  • required: false
  • type: boolean