133dd61578
The Poll* methods predate context in Go, and the current implementation will return ErrWaitTimeout even if the context is cancelled, which prevents callers who are using Poll* from handling that error directly (for instance, if you want to cancel a function in a controlled fashion but still report cleanup errors to logs, you want to know the difference between 'didn't cancel', 'cancelled cleanly', and 'hit an error). This commit adds two new methods that reflect how modern Go uses context in polling while preserving all Kubernetes-specific behavior: PollUntilContextCancel PollUntilContextTimeout These methods can be used for infinite polling (normal context), timed polling (deadline context), and cancellable poll (cancel context). All other Poll/Wait methods are marked as deprecated for removal in the future. The ErrWaitTimeout error will no longer be returned from the Poll* methods, but will continue to be returned from ExponentialBackoff*. Users updating to use these new methods are responsible for converting their error handling as appropriate. A convenience helper `Interrupted(err) bool` has been added that should be used instead of checking `err == ErrWaitTimeout`. In a future release ErrWaitTimeout will be made private to prevent incorrect use. The helper can be used with all polling methods since context cancellation and deadline are semantically equivalent to ErrWaitTimeout. A new `ErrorInterrupted(cause error)` method should be used instead of returning ErrWaitTimeout in custom code. The convenience method PollUntilContextTimeout is added because deadline context creation is verbose and the cancel function must be called to properly cleanup the context - many of the current poll users would see code sizes increase. To reduce the overall method surface area, the distinction between PollImmediate and Poll has been reduced to a single boolean on PollUntilContextCancel so we do not need multiple helper methods. The existing methods were not altered because ecosystem callers have been observed to use ErrWaitTimeout to mean "any error that my condition func did not return" which prevents cancellation errors from being returned from the existing methods. Callers must make a deliberate migration. Callers migrating to `PollWithContextCancel` should: 1. Pass a context with a deadline or timeout if they were previously using `Poll*Until*` and check `err` for `context.DeadlineExceeded` instead of `ErrWaitTimeout` (more specific) or use `Interrupted(err)` for a generic check. 2. Callers that were waiting forever or for context cancellation should ensure they are checking `context.Canceled` instead of `ErrWaitTimeout` to detect when the poll was stopped early. Callers of `ExponentialBackoffWithContext` should use `Interrupted(err)` instead of directly checking `err == ErrWaitTimeout`. No other changes are needed. Code that returns `ErrWaitTimeout` should instead define a local cause and return `wait.ErrorInterrupted(cause)`, which will be recognized by `wait.Interrupted()`. If nil is passed the previous message will be used but clients are highly recommended to use typed checks vs message checks. As a consequence of this change the new methods are more efficient - Poll uses one less goroutine. |
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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.