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Clarify retry.RetryOnConflict docs

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Kubernetes-commit: 23b391e1dd56e84708ac8c95bf6293fe86879c1c
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Dan Winship 2019-09-03 12:26:17 -04:00 committed by Kubernetes Publisher
parent 0e80a77286
commit 9781541482
1 changed files with 28 additions and 9 deletions
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37
util/retry/util.go
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@ -65,18 +65,37 @@ func OnError(backoff wait.Backoff, retriable func(error) bool, fn func() error)
return err
}
// RetryOnConflict executes the function function repeatedly, retrying if the server returns a conflicting
// write. Callers should preserve previous executions if they wish to retry changes. It performs an
// exponential backoff.
// RetryOnConflict is used to make an update to a resource when you have to worry about
// conflicts caused by other code making unrelated updates to the resource at the same
// time. fn should fetch the resource to be modified, make appropriate changes to it, try
// to update it, and return (unmodified) the error from the update function. On a
// successful update, RetryOnConflict will return nil. If the update function returns a
// "Conflict" error, RetryOnConflict will wait some amount of time as described by
// backoff, and then try again. On a non-"Conflict" error, or if it retries too many times
// and gives up, RetryOnConflict will return an error to the caller.
//
// var pod *api.Pod
// err := RetryOnConflict(DefaultBackoff, func() (err error) {
// pod, err = c.Pods("mynamespace").UpdateStatus(podStatus)
// return
// err := retry.RetryOnConflict(retry.DefaultRetry, func() error {
// // Fetch the resource here; you need to refetch it on every try, since
// // if you got a conflict on the last update attempt then you need to get
// // the current version before making your own changes.
// pod, err := c.Pods("mynamespace").Get(name, metav1.GetOptions{})
// if err ! nil {
// return err
// }
//
// // Make whatever updates to the resource are needed
// pod.Status.Phase = v1.PodFailed
//
// // Try to update
// _, err = c.Pods("mynamespace").UpdateStatus(pod)
// // You have to return err itself here (not wrapped inside another error)
// // so that RetryOnConflict can identify it correctly.
// return err
// })
// if err != nil {
// // may be conflict if max retries were hit
// return err
// // May be conflict if max retries were hit, or may be something unrelated
// // like permissions or a network error
// return err
// }
// ...
//