About

To cache images, Kubernetes Image Puller creates a Daemonset on the desired cluster, which in turn creates a pod on each node in the cluster consisting of a list of containers with command sleep 720h. This ensures that all nodes in the cluster have those images cached. The sleep binary being used is golang-based (please see Scratch Images). We also periodically check the health of the daemonset and re-create it if necessary.

The application can be deployed via Helm or by processing and applying OpenShift Templates. Also, there is a community supported operator available on the OperatorHub.

Configuration

Configuration is done via env vars pulled from ./deploy/helm/templates/configmap.yaml, or ./deploy/openshift/configmap.yaml, depending on the deployment method. The config values to be set are:

Env Var	Usage	Default
CACHING_INTERVAL_HOURS	Interval, in hours, between checking health of daemonsets	"1"
CACHING_MEMORY_REQUEST	The memory request for each cached image when the puller is running	10Mi
CACHING_MEMORY_LIMIT	The memory limit for each cached image when the puller is running	20Mi
CACHING_CPU_REQUEST	The CPU request for each cached image when the puller is running	.05 or 50 millicores
CACHING_CPU_LIMIT	The CPU limit for each cached image when the puller is running	.2 or 200 millicores
DAEMONSET_NAME	Name of daemonset to be created	kubernetes-image-puller
NAMESPACE	Namespace where daemonset is to be created	kubernetes-image-puller
IMAGES	List of images to be cached, in the format <name>=<image>;...	Contains a default list of images, but should be configured when deploying
NODE_SELECTOR	Node selector applied to pods created by the daemonset	'{}'
IMAGE_PULL_SECRETS	List of image pull secrets, in the format pullsecret1;... to add to pods created by the DaemonSet. Those secrets need to be in the image puller's namespace and a cluster administrator must create them.	""
AFFINITY	Affinity applied to pods created by the daemonset	'{}'
KIP_IMAGE	The image puller image to copy the sleep binary from	quay.io/eclipse/kubernetes-image-puller:next

Configuration - Helm

The following values can be set:

Value	Usage	Default
deploymentName	The value of DAEMONSET_NAME to be set in the ConfigMap, as well as the name of the deployment	kubernetes-image-puller
image.repository	The repository to pull the image from	quay.io/eclipse/kubernetes-image-puller
image.tag	The image tag to pull	next
serviceAccount.name	The name of the ServiceAccount to create	k8s-image-puller
configMap.name	The name of the ConfigMap to create	k8s-image-puller
configMap.images	The value of IMAGES to be set in the ConfigMap	// TODO create a reasonable set of default containers
configMap.cachingIntervalHours	The value of CACHING_INTERVAL_HOURS to be set in the ConfigMap	"1"
configMap.cachingMemoryRequest	The value of CACHING_MEMORY_REQUEST to be set in the ConfigMap	"10Mi"
configMap.cachingMemoryLimit	The value of CACHING_MEMORY_LIMIT to be set in the ConfigMap	"20Mi"
configMap.cachingCpuRequest	The value of CACHING_CPU_REQUEST to be set in the ConfigMap	.05
configMap.cachingCpuLimit	The value of CACHING_CPU_LIMIT to be set in the ConfigMap	.2
configMap.nodeSelector	The value of NODE_SELECTOR to be set in the ConfigMap	"{}"
configMap.imagePullSecrets	The value of IMAGE_PULL_SECRETS	""
configMap.affinity	The value of AFFINITY to be set in the ConfigMap	"{}"

Configuration - OpenShift

The following values can be set:

Parameter	Usage	Default
SERVICEACCOUNT_NAME	Name of service account used by main pod	k8s-image-puller
IMAGE	Name of image used for main pod	quay.io/eclipse/kubernetes-image-puller
IMAGE_TAG	Tag of image used for main pod	next
DAEMONSET_NAME	The value of DAEMONSET_NAME to be set in the ConfigMap	"kubernetes-image-puller"
DEPLOYMENT_NAME	The name of the image puller deployment	"kubernetes-image-puller"
CACHING_INTERVAL_HOURS	The value of CACHING_INTERVAL_HOURS to be set in the ConfigMap	"1"
CACHING_MEMORY_REQUEST	The value of CACHING_MEMORY_REQUEST to be set in the ConfigMap	"10Mi"
CACHING_MEMORY_LIMIT	The value of CACHING_MEMORY_LIMIT to be set in the ConfigMap	"20Mi"
CACHING_CPU_REQUEST	The value of CACHING_CPU_REQUEST to be set in the ConfigMap	.05
CACHING_CPU_LIMIT	The value of CACHING_CPU_LIMIT to be set in the ConfigMap	.2
NAMESPACE	The value of NAMESPACE to be set in the ConfigMap	k8s-image-puller
NODE_SELECTOR	The value of NODE_SELECTOR to be set in the ConfigMap	"{}"
IMAGE_PULL_SECRETS	The value of IMAGE_PULL_SECRETS	""
AFFINITY	The value of AFFINITY to be set in the ConfigMap	"{}"

Installation - Helm

kubectl create namespace k8s-image-puller

helm install kubernetes-image-puller -n k8s-image-puller deploy/helm

To set values, change deploy/helm/values.yaml or use --set property.name=value

or

helm repo add image-pull https://raw.githubusercontent.com/signcl/kubernetes-image-puller/master/packages

helm install image-puller image-pull/kubernetes-image-puller -f values.yaml

Installation - Openshift

Openshift special consideration - Project Quotas

OpenShift has a notion of project quotas to limit the aggregate resource consumption per project/namespace. The namespace that the image puller is deployed in must have enough memory and CPU to run each container for each node in the cluster:

(memory/CPU limit) * (number of images) * (number of nodes in cluster)

For example, running the image puller that caches 5 images on 20 nodes, with a container memory limit of 5Mi, your namespace would need a quota of 500Mi.

Installing the image puller

oc new-project k8s-image-puller

oc process -f deploy/openshift/serviceaccount.yaml | oc apply -f -

oc process -f deploy/openshift/configmap.yaml | oc apply -f -

oc process -f deploy/openshift/app.yaml | oc apply -f -

To change parameters, add -p PARAM=value to the oc process command, before piping to oc apply.

Building

Makefile

# Build Go binary:
make build
# Make docker image:
make docker
# The above:
make
# Clean:
make clean

The provided Makefile has two parameters:

• DOCKERIMAGE_NAME: name for docker image
• DOCKERIMAGE_TAG: tag for docker image

Manual

Build:

GOOS=linux go build -v -o ./bin/kubernetes-image-puller ./cmd/main.go

Make docker image:

docker build -t ${DOCKERIMAGE_NAME}:${DOCKERIMAGE_TAG} -f ./docker/Dockerfile .

Testing

To run the unit tests:

make test

End to end tests require kind. Note that kind should not be installed with go get from this repository's directory.

cd $HOME && GO111MODULE="on" go get sigs.k8s.io/[email protected] && cd ~-

./hack/run-e2e.sh

Will start a kind cluster and run the end-to-end tests in ./e2e. To remove the cluster after running the tests, pass the --rm argument to the script, or run kind delete cluster --name k8s-image-puller-e2e.

Scratch Images

The image puller now supports pre-pulling scratch images. Previously the image puller was not able to pull scratch images, as they do not contain a sleep command.

However, the daemonset created by the Kubernetes Image Puller now:

1. creates an initContainer that copies a golang-based sleep binary to a common kip volume.
2. creates containers volumeMounts set to the kip volume, and with command set to /kip/sleep 720h

As a result, every container (including scratch image containers) uses the provided golang-based sleep binary.