mirror of https://github.com/k3s-io/k3s
37 lines
1.8 KiB
Markdown
37 lines
1.8 KiB
Markdown
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# Move the ServiceLB load-balancer controller into the K3s cloud provider
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Date: 2022-09-29
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## Status
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Accepted
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## Context
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K3s includes a stub cloud-provider the implements just enough node lifecycle functionality (the
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`cloudprovider.Instances` interface) to get node addresses set properly, and clear the Uninitialized taint
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that is added to nodes when they first join the cluster. The cloud-provider interface also has extension
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points for load-balancer controllers, but we did not implement these, in favor of running a standalone
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ServiceLB controller that is directly hooked into the core Wrangler controllers.
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Because it doesn't make use of the existing load-balancer interface, the ServiceLB controller must implement
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all the logic to watch Services, ensure that it's only handling services of the correct type and state, manage
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finalizers, and so on. This would all be handled by core Kubernetes code if we implemented the
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`cloudprovider.LoadBalancer` interface.
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## Decision
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We will move the ServiceLB code into the cloud-controller, as a backend for the LoadBalancer interface
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implementation. Existing behavior for disabling node lifecycle functionality will be retained, such that users
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can still use ServiceLB alongside other cloud-controller-managers that handle node lifecycle. Support for
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customizing ServiceLB behavior via node labels will be retained.
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## Consequences
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* K3s uses less resources when ServiceLB is disabled, as several core controllers are no longer started
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unconditionally.
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* The `--disable-cloud-controller` flag now disables the CCM's `cloud-node` and `cloud-node-lifecycle`
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controllers that were historically the only supported controllers.
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* The `--disable=servicelb` flag now disables the CCM's `service` controller.
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* If the cloud-controller and servicelb are both disabled, the cloud-controller-manager is not run at all.
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