feb4227788
Also make some design changes exposed in testing and review. Do not remove the ambiguous old metric `apiserver_flowcontrol_request_concurrency_limit` because reviewers though it is too early. This creates a problem, that metric can not keep both of its old meanings. I chose the configured concurrency limit. Testing has revealed a design flaw, which concerns the initialization of the seat demand state tracking. The current design in the KEP is as follows. > Adjustment is also done on configuration change … For a newly > introduced priority level, we set HighSeatDemand, AvgSeatDemand, and > SmoothSeatDemand to NominalCL-LendableSD/2 and StDevSeatDemand to > zero. But this does not work out well at server startup. As part of its construction, the APF controller does a configuration change with zero objects read, to initialize its request-handling state. As always, the two mandatory priority levels are implicitly added whenever they are not read. So this initial reconfig has one non-exempt priority level, the mandatory one called catch-all --- and it gets its SmoothSeatDemand initialized to the whole server concurrency limit. From there it decays slowly, as per the regular design. So for a fairly long time, it appears to have a high demand and competes strongly with the other priority levels. Its Target is higher than all the others, once they start to show up. It properly gets a low NominalCL once other levels show up, which actually makes it compete harder for borrowing: it has an exceptionally high Target and a rather low NominalCL. I have considered the following fix. The idea is that the designed initialization is not appropriate before all the default objects are read. So the fix is to have a mode bit in the controller. In the initial state, those seat demand tracking variables are set to zero. Once the config-producing controller detects that all the default objects are pre-existing, it flips the mode bit. In the later mode, the seat demand tracking variables are initialized as originally designed. However, that still gives preferential treatment to the default PriorityLevelConfiguration objects, over any that may be added later. So I have made a universal and simpler fix: always initialize those seat demand tracking variables to zero. Even if a lot of load shows up quickly, remember that adjustments are frequent (every 10 sec) and the very next one will fully respond to that load. Also: revise logging logic, to log at numerically lower V level when there is a change. Also: bug fix in float64close. Also, separate imports in some file Co-authored-by: Han Kang <hankang@google.com>
Kubernetes (K8s)
Kubernetes, also known as K8s, is an open source system for managing containerized applications across multiple hosts. It provides 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 your company 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 K8s
See our documentation on kubernetes.io.
Try our interactive tutorial.
Take a free course on Scalable Microservices with Kubernetes.
To use Kubernetes code as a library in other applications, see the list of published components.
Use of the k8s.io/kubernetes module or k8s.io/kubernetes/... packages as libraries is not supported.
To start developing K8s
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.
mkdir -p $GOPATH/src/k8s.io
cd $GOPATH/src/k8s.io
git clone https://github.com/kubernetes/kubernetes
cd 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.
Community Meetings
The Calendar has the list of all the meetings in Kubernetes community in a single location.
Adopters
The User Case Studies website has real-world use cases of organizations across industries that are deploying/migrating to Kubernetes.
Governance
Kubernetes project is governed by a framework of principles, values, policies and processes to help our community and constituents towards our shared goals.
The Kubernetes Community is the launching point for learning about how we organize ourselves.
The Kubernetes Steering community repo is used by the Kubernetes Steering Committee, which oversees governance of the Kubernetes project.
Roadmap
The Kubernetes Enhancements repo provides information about Kubernetes releases, as well as feature tracking and backlogs.