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.

Where?

Images are available at:

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

Both are identical multi-arch images built for amd64, arm64 and arm/v7

Features

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

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

name	description	required	default	type
LABEL	Label that should be used for filtering	true	-	string
LABEL_VALUE	The value for the label you want to filter your resources on. Don't set a value to filter by any value	false	-	string
FOLDER	Folder where the files should be placed	true	-	string
FOLDER_ANNOTATION	The annotation the sidecar will look for in configmaps to override the destination folder for files. The annotation value can be either an absolute or a relative path. Relative paths will be relative to FOLDER.	false	k8s-sidecar-target-directory	string
NAMESPACE	Comma separated list of namespaces. If specified, the sidecar will search for config-maps inside these namespaces. It's also possible to specify ALL to search in all namespaces.	false	namespace in which the sidecar is running	string
RESOURCE	Resource type, which is monitored by the sidecar. Options: configmap, secret, both	false	configmap	string
METHOD	If METHOD is set to LIST, the sidecar will just list config-maps/secrets and exit. With SLEEP it will list all config-maps/secrets, then sleep for SLEEP_TIME seconds. Anything else will continuously watch for changes (see https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes).	false	-	string
SLEEP_TIME	How many seconds to wait before updating config-maps/secrets when using SLEEP method.	false	60	integer
REQ_URL	URL to which send a request after a configmap/secret got reloaded	false	-	URI
REQ_METHOD	Request method GET or POST for requests tp REQ_URL	false	GET	string
REQ_PAYLOAD	If you use REQ_METHOD=POST you can also provide json payload	false	-	json
REQ_RETRY_TOTAL	Total number of retries to allow for any http request (*.url triggered requests, requests to REQ_URI and k8s api requests)	false	5	integer
REQ_RETRY_CONNECT	How many connection-related errors to retry on for any http request (*.url triggered requests, requests to REQ_URI and k8s api requests)	false	10	integer
REQ_RETRY_READ	How many times to retry on read errors for any http request (.url triggered requests, requests to REQ_URI and k8s api requests)	false	5	integer
REQ_RETRY_BACKOFF_FACTOR	A backoff factor to apply between attempts after the second try for any http request (.url triggered requests, requests to REQ_URI and k8s api requests)	false	1.1	float
REQ_TIMEOUT	How many seconds to wait for the server to send data before giving up for .url triggered requests or requests to REQ_URI (does not apply to k8s api requests)	false	10	float
REQ_USERNAME	Username to use for basic authentication for requests to REQ_URL and for *.url triggered requests	false	-	string
REQ_PASSWORD	Password to use for basic authentication for requests to REQ_URL and for *.url triggered requests	false	-	string
SCRIPT	Absolute path to shell script to execute after a configmap got reloaded. It runs before calls to REQ_URI	false	-	string
ERROR_THROTTLE_SLEEP	How many seconds to wait before watching resources again when an error occurs	false	5	integer
SKIP_TLS_VERIFY	Set to true to skip tls verification for kube api calls	false	-	boolean
UNIQUE_FILENAMES	Set to true to produce unique filenames where duplicate data keys exist between ConfigMaps and/or Secrets within the same or multiple Namespaces.	false	false	boolean
DEFAULT_FILE_MODE	The default file system permission for every file. Use three digits (e.g. '500', '440', ...)	false	-	string
KUBECONFIG	if this is given and points to a file or ~/.kube/config is mounted k8s config will be loaded from this file, otherwise "incluster" k8s configuration is tried.	false	-	string
ENABLE_5XX	Set to true to enable pulling of 5XX response content from config map. Used in case if the filename ends with .url suffix (Please refer to the *.url feature here.)	false	-	boolean