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Clayton Coleman 133dd61578 wait: Deprecate legacy Poll methods for new context aware methods 
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.
2023-03-14 13:14:11 -06:00
..
publishing
update go to 1.19.7 in publishing bot rules for active release branches
2023-03-10 09:57:14 +01:00
src/k8s.io
wait: Deprecate legacy Poll methods for new context aware methods
2023-03-14 13:14:11 -06:00
OWNERS
Move root approvers to subdirs
2022-10-10 13:43:03 -04:00
README.md
update staging README.md
2023-01-09 12:26:16 +08:00

README.md

External Repository Staging Area

This directory is the staging area for packages that have been split to their own repository. The content here will be periodically published to respective top-level k8s.io repositories.

Repositories currently staged here:

The code in the staging/ directory is authoritative, i.e. the only copy of the code. You can directly modify such code.

Using staged repositories from Kubernetes code

Kubernetes code uses the repositories in this directory via symlinks in the vendor/k8s.io directory into this staging area. For example, when Kubernetes code imports a package from the k8s.io/client-go repository, that import is resolved to staging/src/k8s.io/client-go relative to the project root:

// pkg/example/some_code.go
package example

import (
  "k8s.io/client-go/dynamic" // resolves to staging/src/k8s.io/client-go/dynamic
)

Once the change-over to external repositories is complete, these repositories will actually be vendored from k8s.io/<package-name>.

Creating a new repository in staging

Adding the staging repository in kubernetes/kubernetes:

  1. Send an email to the SIG Architecture mailing list and the mailing list of the SIG which would own the repo requesting approval for creating the staging repository.

  2. Once approval has been granted, create the new staging repository.

  3. Add a symlink to the staging repo in vendor/k8s.io.

  4. Update import-restrictions.yaml to add the list of other staging repos that this new repo can import.

  5. Add all mandatory template files to the staging repo as mentioned in https://github.com/kubernetes/kubernetes-template-project.

  6. Make sure that the .github/PULL_REQUEST_TEMPLATE.md and CONTRIBUTING.md files mention that PRs are not directly accepted to the repo.

  7. Ensure that docs.go file is added. Refer to #kubernetes/kubernetes#91354 for reference.

  8. NOTE: Do not edit go.mod or go.sum in the new repo (staging/src/k8s.io//) manually. Run the following instead:

  ./hack/update-vendor.sh

Creating the published repository

  1. Create an issue in the kubernetes/org repo to request creation of the respective published repository in the Kubernetes org. The published repository must have an initial empty commit. It also needs specific access rules and branch settings. See #kubernetes/org#58 for an example.

  2. Setup branch protection and enable access to the stage-bots team by adding the repo in prow/config.yaml. See #kubernetes/test-infra#9292 for an example.

  3. Once the repository has been created in the Kubernetes org, update the publishing-bot to publish the staging repository by updating:

    • rules.yaml: Make sure that the list of dependencies reflects the staging repos in the Godeps.json file.

    • repos.sh: Add the staging repo in the list of repos to be published.

  4. Add the staging and published repositories as a subproject for the SIG that owns the repos in sigs.yaml.

  5. Add the repo to the list of staging repos in this README.md file.