Impact of losing etcd quorum
WHAT IT TESTS: control vs data plane separation. OUTLINE: without quorum etcd goes read-only-ish and the API server cannot persist writes, so scheduling and changes stall, but kubelets keep running existing pods.
WHAT IT TESTS: that the control plane and data plane fail independently. ANSWER OUTLINE: losing etcd quorum means no leader can commit writes, so the API server rejects creates, updates and deletes; scheduling, scaling, deployments and most controller actions halt. The data plane keeps going: kubelets continue running already-scheduled pods and kube-proxy keeps routing, because they act on local state. Self-healing and rescheduling stop. RED FLAG: asserting running workloads immediately crash when quorum is lost.
Read the original → interview
- #kubernetes
- #etcd
- #control-plane
- #quorum
- #reliability
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