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https://issues.apache.org/jira/browse/CASSANDRA-21541?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18100235#comment-18100235
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Dmitry Konstantinov commented on CASSANDRA-21541:
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+1, thank you!
> CI: cache Docker Hub image pulls in-cluster for the k8s Jenkins agents
> ----------------------------------------------------------------------
>
> Key: CASSANDRA-21541
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21541
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: CI
> Reporter: Michael Semb Wever
> Assignee: Michael Semb Wever
> Priority: Normal
>
> In a Helm deployed CI, each CI agent runs its own docker-in-docker daemon
> on an emptyDir, blank to begin with. Every agent therefore pulls the same
> build and test images afresh; the largest, `cassandra-ubuntu-test`, is ~35Gi.
> At hundreds of concurrent agents this is slow, wastes bandwidth, and trips
> pull-rate limits.
> Add an in-cluster Docker Hub pull-through cache (a registry:2 proxy) and
> point the agents' `dind` at it via `--registry-mirror`. Each image is then
> fetched from Docker Hub once and served to every agent over the cluster LAN;
> `dind` falls back to Docker Hub directly if the cache is unreachable.
> Docker's `--registry-mirror` can only mirror Docker Hub, not an arbitrary
> registry such as apache.jfrog.io. So the prefetch in the Jenkinsfile is
> repointed from the apache.jfrog.io names to those same Docker Hub names.
> Patch changes:
> - `.jenkins/k8s/docker-cache.yaml`: the pull-through cache (Deployment,
> Service, PVC), pinned to the always-on controller node.
> - `.jenkins/k8s/jenkins-deployment.yaml`: `dind` `--registry-mirror` in all
> three agent templates.
> - `.build/run-ci`: `--setup/--only-setup` applies the cache; teardown
> removes it.
> - `.jenkins/Jenkinsfile`: prefetch the Docker Hub image names.
> The cache runs a single replica for now. It converts repeated WAN pulls
> into one origin fetch plus LAN reads; if the pod's egress becomes the
> bottleneck this can be scaled with replicas or an object-storage backend.
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