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chore(kb/eks): improve notes about autoscaling

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Michele Cereda
2025-01-06 17:40:07 +01:00
parent f90e1619c4
commit 303d54302f
3 changed files with 124 additions and 4 deletions
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knowledge base/kubernetes/cluster autoscaler.md
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@@ -4,6 +4,8 @@ Automatically adjusts the number of nodes in Kubernetes clusters to meet their c
1. [TL;DR](#tldr)
1. [Best practices](#best-practices)
1. [Troubleshooting](#troubleshooting)
1. [Unschedulable pods do not trigger scale-up](#unschedulable-pods-do-not-trigger-scale-up)
1. [Further readings](#further-readings)
1. [Sources](#sources)
@@ -62,11 +64,31 @@ aws eks --region 'eu-west-1' update-kubeconfig --name 'custom-eks-cluster' \
## Best practices
- Do **not** modify nodes belonging to autoscaled node groups directly.
Changes will be soon lost as the modified nodes might be deleted at any time.
- All nodes within the same autoscaled node group should have the same capacity, labels and system pods running on them.
- Specify requests for all the pods one can.
- Specify resource requests for all the pods one can, so that nodes can be scaled more reliably.
- Should one need to prevent pods from being deleted too abruptly, consider using PodDisruptionBudgets.
- Check one's cloud provider's quota is big enough **before** specifying min/max settings for clusters' node pools.
- Do **not** run **any** additional node group autoscaler (**especially** those from one's own cloud provider).
- Check one's cloud provider's VM quota is big enough **before** specifying min/max settings for clusters' node pools.
- Ensure **any** additional node group autoscaler (**especially** those from one's own cloud provider) are **not**
competing for resources.<br/>
- Prefer **avoiding** running multiple node autoscalers if possible.
## Troubleshooting
### Unschedulable pods do not trigger scale-up
#### Context <!-- omit in toc -->
As of 2025-01-06, at least with EKS, it easily happens that unschedulable pods that would normally trigger a scale-up
stay unschedulable and cause the _pod didn't trigger scale-up_ event instead.
This primarily happens when the cluster's node groups are updated for any reason.
#### Solution <!-- omit in toc -->
Restarting the Cluster Autoscaler's pods worked most of the time.
It seems to be some sort of issue with cache.
## Further readings