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Merge pull request #59159 from roycaihw/dfifo 

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Add comments about potential race in delta fifo

**What this PR does / why we need it**:

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

/sig api-machinery
pull/6/head
Kubernetes Submit Queue 2018-02-24 20:46:31 -08:00 committed by GitHub
parent f49f799dbd 8b03e77aec
commit 0394ffba6d
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 16 additions and 7 deletions
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23
staging/src/k8s.io/client-go/tools/cache/delta_fifo.go vendored
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@ -38,9 +38,22 @@ import (
// TODO: consider merging keyLister with this object, tracking a list of
// "known" keys when Pop() is called. Have to think about how that
// affects error retrying.
// TODO(lavalamp): I believe there is a possible race only when using an
// external known object source that the above TODO would
// fix.
// NOTE: It is possible to misuse this and cause a race when using an
// external known object source.
// Whether there is a potential race depends on how the comsumer
// modifies knownObjects. In Pop(), process function is called under
// lock, so it is safe to update data structures in it that need to be
// in sync with the queue (e.g. knownObjects).
//
// Example:
// In case of sharedIndexInformer being a consumer
// (https://github.com/kubernetes/kubernetes/blob/0cdd940f/staging/
// src/k8s.io/client-go/tools/cache/shared_informer.go#L192),
// there is no race as knownObjects (s.indexer) is modified safely
// under DeltaFIFO's lock. The only exceptions are GetStore() and
// GetIndexer() methods, which expose ways to modify the underlying
// storage. Currently these two methods are used for creating Lister
// and internal tests.
//
// Also see the comment on DeltaFIFO.
func NewDeltaFIFO(keyFunc KeyFunc, knownObjects KeyListerGetter) *DeltaFIFO {
@ -199,8 +212,6 @@ func (f *DeltaFIFO) Delete(obj interface{}) error {
if err == nil && !exists && !itemsExist {
// Presumably, this was deleted when a relist happened.
// Don't provide a second report of the same deletion.
// TODO(lavalamp): This may be racy-- we aren't properly locked
// with knownObjects.
return nil
}
}
@ -485,8 +496,6 @@ func (f *DeltaFIFO) Replace(list []interface{}, resourceVersion string) error {
}
// Detect deletions not already in the queue.
// TODO(lavalamp): This may be racy-- we aren't properly locked
// with knownObjects. Unproven.
knownKeys := f.knownObjects.ListKeys()
queuedDeletions := 0
for _, k := range knownKeys {