80e279d353
This change adds pending pods to the ignored set first before selecting pods missing metrics. Pending pods are always ignored when calculating scale. When the HPA decides which pods and metric values to take into account when scaling, it divides the pods into three disjoint subsets: 1) ready 2) missing metrics and 3) ignored. First the HPA selects pods which are missing metrics. Then it selects pods should be ignored because they are not ready yet, or are still consuming CPU during initialization. All the remaining pods go into the ready set. After the HPA has decided what direction it wants to scale based on the ready pods, it considers what might have happened if it had the missing metrics. It makes a conservative guess about what the missing metrics might have been, 0% if it wants to scale up--100% if it wants to scale down. This is a good thing when scaling up, because newly added pods will likely help reduce the usage ratio, even though their metrics are missing at the moment. The HPA should wait to see the results of its previous scale decision before it makes another one. However when scaling down, it means that many missing metrics can pin the HPA at high scale, even when load is completely removed. In particular, when there are many unschedulable pods due to insufficient cluster capacity, the many missing metrics (assumed to be 100%) can cause the HPA to avoid scaling down indefinitely. |
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| WORKSPACE | ||
Kubernetes
Kubernetes is an open source system for managing containerized applications across multiple hosts; providing basic mechanisms for deployment, maintenance, and scaling of applications.
Kubernetes builds upon a decade and a half of experience at Google running production workloads at scale using a system called Borg, combined with best-of-breed ideas and practices from the community.
Kubernetes is hosted by the Cloud Native Computing Foundation (CNCF). If you are a company that wants to help shape the evolution of technologies that are container-packaged, dynamically-scheduled and microservices-oriented, consider joining the CNCF. For details about who's involved and how Kubernetes plays a role, read the CNCF announcement.
To start using Kubernetes
See our documentation on kubernetes.io.
Try our interactive tutorial.
Take a free course on Scalable Microservices with Kubernetes.
To start developing Kubernetes
The community repository hosts all information about building Kubernetes from source, how to contribute code and documentation, who to contact about what, etc.
If you want to build Kubernetes right away there are two options:
You have a working Go environment.
go get -d k8s.io/kubernetes
cd $GOPATH/src/k8s.io/kubernetes
make
You have a working Docker environment.
git clone https://github.com/kubernetes/kubernetes
cd kubernetes
make quick-release
For the full story, head over to the developer's documentation.
Support
If you need support, start with the troubleshooting guide, and work your way through the process that we've outlined.
That said, if you have questions, reach out to us one way or another.