Chapter 10. Cache images for faster workspace start

Procedure

1. Gather a list of relevant container images to pull. See Section 10.7, “Retrieve the default list of images for Kubernetes Image Puller”.

2. Define the memory requests and limits parameters to ensure pulled containers and the platform have enough memory to run.

   When defining the minimal value for CACHING_MEMORY_REQUEST or CACHING_MEMORY_LIMIT, consider the necessary amount of memory required to run each of the container images to pull.

   When defining the maximal value for CACHING_MEMORY_REQUEST or CACHING_MEMORY_LIMIT, consider the total memory allocated to the DaemonSet Pods in the cluster:

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

   Pulling 5 images on 20 nodes, with a container memory limit of 20Mi requires 2000Mi of memory.

3. Clone the Image Puller repository and get in the directory containing the OpenShift templates:

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

4. Configure the app.yaml, configmap.yaml, and serviceaccount.yaml OpenShift templates using the following parameters:

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   Table 10.1. Image Puller OpenShift templates parameters in app.yaml

   Value	Usage	Default
   DEPLOYMENT_NAME	The value of DEPLOYMENT_NAME in the ConfigMap	kubernetes-image-puller
   IMAGE	Image used for the kubernetes-image-puller deployment	registry.redhat.io/devspaces/imagepuller-rhel8
   IMAGE_TAG	The image tag to pull	latest
   SERVICEACCOUNT_NAME	The name of the ServiceAccount created and used by the deployment	kubernetes-image-puller

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   Table 10.2. Image Puller OpenShift templates parameters in configmap.yaml

   Value	Usage	Default
   CACHING_CPU_LIMIT	The value of CACHING_CPU_LIMIT in the ConfigMap	.2
   CACHING_CPU_REQUEST	The value of CACHING_CPU_REQUEST in the ConfigMap	.05
   CACHING_INTERVAL_HOURS	The value of CACHING_INTERVAL_HOURS in the ConfigMap	"1"
   CACHING_MEMORY_LIMIT	The value of CACHING_MEMORY_LIMIT in the ConfigMap	"20Mi"
   CACHING_MEMORY_REQUEST	The value of CACHING_MEMORY_REQUEST in the ConfigMap	"10Mi"
   DAEMONSET_NAME	The value of DAEMONSET_NAME in the ConfigMap	kubernetes-image-puller
   DEPLOYMENT_NAME	The value of DEPLOYMENT_NAME in the ConfigMap	kubernetes-image-puller
   IMAGES	The value of IMAGES in the ConfigMap	{}
   NAMESPACE	The value of NAMESPACE in the ConfigMap	k8s-image-puller
   NODE_SELECTOR	The value of NODE_SELECTOR in the ConfigMap	"{}"

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   Table 10.3. Image Puller OpenShift templates parameters in serviceaccount.yaml

   Value	Usage	Default
   SERVICEACCOUNT_NAME	The name of the ServiceAccount created and used by the deployment	kubernetes-image-puller
   KIP_IMAGE	The image puller image to copy the sleep binary from	registry.redhat.io/devspaces/imagepuller-rhel8:latest

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5. Create an OpenShift project to host the Image Puller:

   oc new-project <k8s-image-puller>

6. Process and apply the templates to install the puller:

   oc process -f serviceaccount.yaml | oc apply -f -
   oc process -f configmap.yaml | oc apply -f -
   oc process -f app.yaml | oc apply -f -

Verification

1. Verify the existence of a <kubernetes-image-puller> deployment and a <kubernetes-image-puller> DaemonSet. The DaemonSet needs to have a Pod for each node in the cluster:

   oc get deployment,daemonset,pod --namespace <k8s-image-puller>

2. Verify the values of the <kubernetes-image-puller> ConfigMap.

   oc get configmap <kubernetes-image-puller> --output yaml

Procedure

1. Install the Kubernetes Image Puller Operator. See Installing from OperatorHub using the web console.
2. Create a KubernetesImagePuller operand from the Kubernetes Image Puller Operator. See Creating applications from installed Operators.

Procedure

1. Configure the Image Puller to pre-pull OpenShift Dev Spaces images.

   oc patch checluster/devspaces \
       --namespace openshift-devspaces \
       --type='merge' \
       --patch '{
                 "spec": {
                   "components": {
                     "imagePuller": {
                       "enable": true
                     }
                   }
                 }
               }'

Procedure

1. Configure the Image Puller to pre-pull custom images.

   oc patch checluster/devspaces \
       --namespace openshift-devspaces \
       --type='merge' \
       --patch '{
                 "spec": {
                   "components": {
                     "imagePuller": {
                       "enable": true,
                       "spec": {
                         "images": "NAME-1=IMAGE-1;NAME-2=IMAGE-2"
                       }
                     }
                   }
                 }
               }'

   where:

   images

   The semicolon-separated list of images in name=image format.

Procedure

1. Create k8s-image-puller namespace:

   oc create namespace k8s-image-puller

2. Create KubernetesImagePuller Custom Resource:

   oc apply -f - <<EOF
   apiVersion: che.eclipse.org/v1alpha1
   kind: KubernetesImagePuller
   metadata:
     name: k8s-image-puller-images
     namespace: k8s-image-puller
   spec:
     images: "NAME-1=IMAGE-1;NAME-2=IMAGE-2"
   EOF

   where:

   images

   The semicolon-separated list of images in name=image format.

Procedure

1. Determine the namespace where the OpenShift Dev Spaces Operator is deployed:

   OPERATOR_NAMESPACE=$(oc get pods -l app.kubernetes.io/component=devspaces-operator -o jsonpath={".items[0].metadata.namespace"} --all-namespaces)

2. Determine the images that can be pre-pulled by the Image Puller:

   oc exec -n $OPERATOR_NAMESPACE deploy/devspaces-operator -- cat /tmp/external_images.txt