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Rescheduler Doc changes (#8906)

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* Rescheduler Doc changes

Rescheduler now works with only DaemonSet pods.

* Update guaranteed-scheduling-critical-addon-pods.md
This commit is contained in:
RaviSantosh Gudimetla
2018-06-04 21:47:54 -04:00
committed by k8s-ci-robot
parent d40e4af148
commit 11089d602d
1 changed files with 5 additions and 3 deletions
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content/en/docs/tasks/administer-cluster/guaranteed-scheduling-critical-addon-pods.md
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@@ -18,19 +18,19 @@ and becomes pending (for example when the cluster is highly utilized and either
vacated by the evicted critical add-on pod or the amount of resources available on the node changed for some other reason). vacated by the evicted critical add-on pod or the amount of resources available on the node changed for some other reason).
## Rescheduler: guaranteed scheduling of critical add-ons ## Rescheduler: guaranteed scheduling of critical add-ons
**Rescheduler is deprecated as of Kubernetes 1.10 and will be removed in version 1.11 in **Rescheduler is deprecated as of Kubernetes 1.10 and will be removed in version 1.12 in
accordance with the [deprecation policy](/docs/reference/deprecation-policy) for beta features.** accordance with the [deprecation policy](/docs/reference/deprecation-policy) for beta features.**
**To avoid eviction of critical pods, you must **To avoid eviction of critical pods, you must
[enable priorities in scheduler](/docs/concepts/configuration/pod-priority-preemption/) [enable priorities in scheduler](/docs/concepts/configuration/pod-priority-preemption/)
before upgrading to Kubernetes 1.10 or higher.** before upgrading to Kubernetes 1.10 or higher.**
Rescheduler ensures that critical add-ons are always scheduled Rescheduler ensures that critical pods created by DaemonSet controller are always scheduled
(assuming the cluster has enough resources to run the critical add-on pods in the absence of regular pods). (assuming the cluster has enough resources to run the critical add-on pods in the absence of regular pods).
If the scheduler determines that no node has enough free resources to run the critical add-on pod If the scheduler determines that no node has enough free resources to run the critical add-on pod
given the pods that are already running in the cluster given the pods that are already running in the cluster
(indicated by critical add-on pod's pod condition PodScheduled set to false, the reason set to Unschedulable) (indicated by critical add-on pod's pod condition PodScheduled set to false, the reason set to Unschedulable)
the rescheduler tries to free up space for the add-on by evicting some pods; then the scheduler will schedule the add-on pod. the rescheduler tries to free up space for the DaemonSet critical pod by evicting some pods; then the scheduler will schedule the add-on pod.
To avoid situation when another pod is scheduled into the space prepared for the critical add-on, To avoid situation when another pod is scheduled into the space prepared for the critical add-on,
the chosen node gets a temporary taint "CriticalAddonsOnly" before the eviction(s) the chosen node gets a temporary taint "CriticalAddonsOnly" before the eviction(s)
@@ -55,6 +55,8 @@ To be considered critical, the pod has to run in the `kube-system` namespace (co
The first one marks a pod a critical. The second one is required by Rescheduler algorithm. The first one marks a pod a critical. The second one is required by Rescheduler algorithm.
A pod could also be considered critical, if its priority is greater than or equal to system-critical-priority.
### Marking pod as critical when priorites are enabled. ### Marking pod as critical when priorites are enabled.
To be considered critical, the pod has to run in the `kube-system` namespace (configurable via flag) and To be considered critical, the pod has to run in the `kube-system` namespace (configurable via flag) and