ramsrib/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. The contained Python script is working from 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 with your 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 an HTTP 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

• LABEL_VALUE

  • description: The value for the label you want to filter your resources on. Don't set a value to filter by any value
  • required: false
  • 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. With SLEEP it will list all config-maps, then sleep for 60 seconds. 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_USERNAME

  • description: Username to use for basic authentication
  • required: false
  • type: string

• 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_PASSWORD

  • description: Password to use for basic authentication
  • required: false
  • type: string

• 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

• DEFAULT_FILE_MODE

  • description: The default file system permission for every file. Use three digits (e.g. '500', '440', ...)
  • required: false
  • type: string