| // caching-images-for-faster-workspace-start |
| |
| [id="image-puller-overview_{context}"] |
| = Image Puller overview |
| |
| Slow starts of {prod} 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 _Image Puller_ can be used to pre-pull images and shorten workspace start times. |
| |
| The Image Puller is an additional deployment that runs alongside {prod}. 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. |
| |
| NOTE: The minimal requirement for an image to be pre-pulled is the availability of the `sleep` command, which means that `FROM scratch` images (for example, 'che-machine-exec') are currently not supported. Also, images that mount volumes in the dockerfile are not supported for pre-pulling on OpenShift. |
| |
| The application can be deployed via Helm or by processing and applying OpenShift templates. |
| |
| The Image Puller pulls its configuration from a `ConfigMap` with the following available parameters: |
| |
| [id="image-puller-configuration_{context}"] |
| .Image Puller default parameters |
| [options="header"] |
| |=== |
| |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. Before deploying, fill this with the images that fit the current requirements |
| |`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. |
