Caching images for faster workspace start | Eclipse Che Documentation

This section describes installing the Kubernetes Image Puller on a Che cluster to cache images on cluster nodes.

Kubernetes Image Puller overview

Slow starts of Eclipse Che workspaces may be caused by waiting for the underlying cluster to pull images used in workspaces from remote registries. As such, pre-pulling images can improve start times significantly. The Kubernetes Image Puller can be used to pre-pull images and shorten workspace start times.

The Kubernetes Image Puller is an additional deployment that runs alongside Eclipse Che. Given a list of images to pre-pull, the application runs inside a cluster and creates a DaemonSet that pulls the images on each node.

The application can be deployed via Helm or by processing and applying OpenShift templates.

The Kubernetes Image Puller pulls its configuration from a ConfigMap with the following available parameters:

Table 1. Kubernetes Image Puller parameters
Parameter	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`
`DAEMONSET_NAME`	Name of DaemonSet to be created	`kubernetes-image-puller`
`NAMESPACE`	Namespace where DaemonSet is to be created	`k8s-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 the Pods created by the DaemonSet	`'{}'`

The default memory requests and limits ensure that the container has enough memory to start. When changing CACHING_MEMORY_REQUEST or CACHING_MEMORY_LIMIT, you will need to consider the total memory allocated to the DaemonSet Pods in the cluster:

(memory limit) * (number of images) * (number of nodes in the cluster)

For example, running the image puller that caches 5 images on 20 nodes, with a container memory limit of 20Mi requires 2000Mi of memory.

Deploying the Kubernetes Image Puller using OpenShift templates

The Kubernetes Image Puller repository contains OpenShift templates for deploying on OpenShift.

Alternatively, you can use Helm for deploying the Kubernetes Image Puller to OpenShift.

Prerequisites

An OpenShift cluster to install to.
The oc binary.

The following parameters are available to further configure the OpenShift templates:

Table 2. Parameters for installing with OpenShift templates
Value	Usage	Default
`DAEMONSET_NAME`	The value of `DAEMONSET_NAME` to be set in the ConfigMap	`kubernetes-image-puller`
`IMAGE`	Image used for the `kubernetes-image-puller` deployment	`quay.io/eclpise/kubernetes-image-puller`
`IMAGE_TAG`	The image tag to pull	`latest`
`SERVICEACCOUNT_NAME`	The name of the ServiceAccount used by the deployment (created as part of installation)	`k8s-image-puller`
`CACHING_INTERVAL_HOURS`	The value of `CACHING_INTERVAL_HOURS` to be set in the ConfigMap	`"1"`
`CACHING_INTERVAL_REQUEST`	The value of `CACHING_MEMORY_REQUEST` to be set in the ConfigMap	`"10Mi"`
`CACHING_INTERVAL_LIMIT`	The value of `CACHING_MEMORY_LIMIT` to be set in the ConfigMap	"20Mi"`
`NODE_SELECTOR`	The value of `NODE_SELECTOR` to be set in the ConfigMap	`"{}"`

See Kubernetes Image Puller parameters for more information about configuration values, such as DAEMONSET_NAME, CACHING_INTERVAL_HOURS, and CACHING_MEMORY_REQUEST.

Procedure

Installing

Clone the kubernetes-image-puller repository:

$ git clone https://github.com/che-incubator/kubernetes-image-puller
$ cd kubernetes-image-puller

Log into the OpenShift cluster and create a namespace to deploy the puller into:

$ oc login -u username -p password https://openshift-cluster-api:6443

$ oc create namespace k8s-image-puller

Process and apply the templates:

$ for template in $(ls deploy/openshift); \
  do oc process -f deploy/openshift/$template | oc apply -f -; done
deployment.apps/kubernetes-image-puller created
configmap/k8s-image-puller created
role.rbac.authorization.k8s.io/create-daemonset created
rolebinding.rbac.authorization.k8s.io/create-daemonset created
serviceaccount/k8s-image-puller created

To set different values than the defaults, use:

$ oc process -p <parameterName>=<value> -f deploy/openshift/<template> | oc apply -f -

Verifying the installation

Confirm that a new deployment, kubernetes-image-puller, and a DaemonSet (named based on the value of the DAEMONSET_NAME parameter) exist. The DaemonSet needs to have a Pod for each node in the cluster:

$ oc get deployment,daemonset,pod --namespace k8s-image-puller
deployment.extensions/kubernetes-image-puller   1/1       1            1           2m19s

NAME                                           DESIRED   CURRENT   READY     UP-TO-DATE   AVAILABLE   NODE SELECTOR   AGE
daemonset.extensions/kubernetes-image-puller   1         1         1         1            1           <none>          2m10s

NAME                                           READY     STATUS    RESTARTS   AGE
pod/kubernetes-image-puller-5495f46497-mkd4p   1/1       Running   0          2m18s
pod/kubernetes-image-puller-n8bmf              3/3       Running   0          2m10s

Check that the ConfigMap named k8s-image-puller has the values you specified in your parameter substitution, or that they contain the default values:

$ oc get configmap k8s-image-puller --output yaml
apiVersion: v1
data:
  CACHING_INTERVAL_HOURS: "1"
  CACHING_MEMORY_LIMIT: 20Mi
  CACHING_MEMORY_REQUEST: 10Mi
  DAEMONSET_NAME: kubernetes-image-puller
  IMAGES: |
    java11-maven=quay.io/eclipse/che-java11-maven:nightly; che-theia=eclipse/che-theia:next; java-plugin-runner=eclipse/che-remote-plugin-runner-java8:latest;
  NAMESPACE: k8s-image-puller
  NODE_SELECTOR: '{}'
kind: ConfigMap
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","data":{"CACHING_INTERVAL_HOURS":"1","CACHING_MEMORY_LIMIT":"20Mi","CACHING_MEMORY_REQUEST":"10Mi","DAEMONSET_NAME":"kubernetes-image-puller","IMAGES":"java11-maven=quay.io/eclipse/che-java11-maven:nightly; che-th
eia=eclipse/che-theia:next; java-plugin-runner=eclipse/che-remote-plugin-runner-java8:latest;\n","NAMESPACE":"k8s-image-puller","NODE_SELECTOR":"{}"},"kind":"ConfigMap","metadata":{"annotations":{},"name":"k8s-image-puller","namespace":"k
8s-image-puller"},"type":"Opaque"}
  creationTimestamp: 2020-02-17T22:40:13Z
  name: k8s-image-puller
  namespace: k8s-image-puller
  resourceVersion: "72250"
  selfLink: /api/v1/namespaces/k8s-image-puller/configmaps/k8s-image-puller
  uid: 76430ed6-51d6-11ea-9c19-52fdfc072182

Deploying the Kubernetes Image Puller using Helm

The Kubernetes Image Puller can be installed using Helm.

Prerequisites

The helm binary
An OpenShift or Kubernetes cluster to install to
The oc or the kubectl binary

In the instructions below, use the oc command when installing on OpenShift and the kubectl command for installing on Kubernetes.

The following parameters are available for configuring the installation with Helm:

Table 3. Parameters for installing with Helm
Value	Usage	Default
`appName`	The value of `DAEMONSET_NAME` to be set in the ConfigMap	`kubernetes-image-puller`
`image.repository`	The repository to pull the image from	`quay.io/eclpise/kubernetes-image-puller`
`image.tag`	The image tag to pull	`latest`
`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.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.cachingMemeryLimit`	The value of `CACHING_MEMORY_LIMIT` to be set in the ConfigMap	"20Mi"`
`configMap.nodeSelector`	The value of `NODE_SELECTOR` to be set in the ConfigMap	`"{}"`

Procedure

Installing

Clone the kubernetes-image-puller repository:

$ git clone https://github.com/che-incubator/kubernetes-image-puller
$ cd kubernetes-image-puller

Create a namespace to deploy the puller into:
```
$ oc create namespace k8s-image-puller
```
Run helm install:
```
$ helm install kubernetes-image-puller --namespace k8s-image-puller deploy/helm
```
To set values, edit the deploy/helm/values.yaml file, or use the --set property.name=<value> parameter.

Verifying the installation

$ oc get deployment,daemonset,pod --namespace k8s-image-puller
NAME                                      READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/kubernetes-image-puller   1/1     1            1           4m21s

NAME                                     DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR   AGE
daemonset.apps/kubernetes-image-puller   3         3         3       3            3           <none>          3m40s

NAME                                          READY   STATUS    RESTARTS   AGE
pod/kubernetes-image-puller-b556c8bd4-qxwwl   1/1     Running   0          4m21s
pod/kubernetes-image-puller-glh87             3/3     Running   0          3m40s
pod/kubernetes-image-puller-h7lxf             3/3     Running   0          3m40s
pod/kubernetes-image-puller-nrt6p             3/3     Running   0          3m40s

Check that the ConfigMap named k8s-image-puller has the values specified in the Helm configuration, or that they contain the default values:

$ oc get configmap k8s-image-puller --output yaml
apiVersion: v1
data:
  CACHING_INTERVAL_HOURS: "1"
  CACHING_MEMORY_LIMIT: 20Mi
  CACHING_MEMORY_REQUEST: 10Mi
  DAEMONSET_NAME: kubernetes-image-puller
  IMAGES: java11-maven=quay.io/eclipse/che-java11-maven:nightly; che-theia=eclipse/che-theia:next;
    java-plugin-runner=eclipse/che-remote-plugin-runner-java8:latest;
  NAMESPACE: k8s-image-puller
  NODE_SELECTOR: '{}'
kind: ConfigMap
metadata:
  creationTimestamp: "2020-02-17T22:15:22Z"
  name: k8s-image-puller
  namespace: k8s-image-puller
  resourceVersion: "3078"
  selfLink: /api/v1/namespaces/k8s-image-puller/configmaps/k8s-image-puller
  uid: 71bc5ce4-d095-468e-ab7b-23c1e0a36638

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