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The certificate manager originally had a "block on startup" rotation behavior to ensure at least one rotation happened on startup. However, since rotation may not succeed within the first time window the code was changed to simply print the error rather than return it. This meant that the blocking rotation has no purpose - it cannot cause the kubelet to fail, and it *does* block the kubelet from starting static pods before the api server becomes available. The current block behavior causes a bootstrapped kubelet that is also set to run static pods to wait several minutes before actually launching the static pods, which means self-hosted masters using static pods have a pointless delay on startup. Since blocking rotation has no benefit and can't actually fail startup, this commit removes the blocking behavior and simplifies the code at the same time. The goroutine for rotation now completely owns the deadline, the shouldRotate() method is removed, and the method that sets rotationDeadline now returns it. We also explicitly guard against a negative sleep interval and omit the message. Should have no impact on bootstrapping except the removal of a long delay on startup before static pods start. Also add a guard condition where if the current cert in the store is expired, we fall back to the bootstrap cert initially (we use the bootstrap cert to communicate with the server). This is consistent with when we don't have a cert yet.
Kubernetes
Kubernetes is an open source system for managing containerized applications across multiple hosts, providing basic mechanisms for deployment, maintenance, and scaling of applications.
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