Cleanup old docker images to free up disk space and inodes
Docker Image Cleaner
A Python package (
docker-image-cleaner) and associated Docker image
quay.io/jupyterhub/docker-image-cleaner) to clean up old docker images when a
disk is running low on inodes or space.
The script has initially been developed to help installations of BinderHub clean up space on nodes as it otherwise can run out of space and stop being able to build now docker images.
Container images are one of the biggest consumers of disk space and inodes on kubernetes nodes. Kubernetes tries to make sure there is enough disk space on each node by garbage collecting unused container images and containers. Tuning this is important for binderhub installations, as many images are built and used only a couple times. However, on most managed kubernetes installations (like GKE, EKS, etc), we can not tune these parameters!
This script approximates the specific parts of the kubernetes container image garbage collection in a configurable way.
- Only kubernetes nodes using the
dockerruntime are supported.
cri-ocontainer backends are not supported.
- The script expects to run in a kubernetes
/var/lib/dockerfrom the node mounted inside the container. This lets the script figure out how much disk space docker container images are actually using.
DaemonSetshould have a
ServiceAccountattached that has permissions to talk to the kubernetes API and cordon / uncordon nodes. This makes sure new pods are not scheduled on to the node while image cleaning is happening, as it can take a while.
How does it work?
- Compute how much space
/var/lib/dockerdirectory (specified by the
DOCKER_IMAGE_CLEANER_PATH_TO_CHECKenvironment variable) is taking up.
- If the disk space used is greater than the garbage collection trigger threshold
DOCKER_IMAGE_CLEANER_THRESHOLD_HIGH), garbage collection is triggered. If not, the script just waits another 5 minutes (set by
- If garbage collection is triggered, the kubernetes node is first cordoned to prevent any new pods from being scheduled on it for the duration of the garbage collection.
- Stopped containers are removed via
docker container prune.
- Dangling images are removed via
docker image prune
- If no dangling images are found to prune, all images are pruned (
docker image prune -a)
- After the garbage collection is done, the kubernetes node is also uncordoned.
- When done, we wait another 5 minutes (set by
DOCKER_IMAGE_CLEANER_INTERVAL_SECONDS), and repeat the whole process.
Currently, environment variables are used to set configuration for now.
||The k8s node where the docker image cleaner is running, so it can be cordoned via the k8s api|
||Amount of time (in seconds) to wait between checking if GC needs to be triggered||
||Amount of time (in seconds) to wait between deleting container images, so we don't DOS the docker API||
||Determine if GC should be triggered based on relative or absolute disk usage||
||% or absolute disk space available (based on
||Request timeout (in seconds) for docker API requests. Pruning images often takes minutes. Default: 300 (5 minutes)|
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