🐛 set partialmetadata gvk in list/watch funcs to avoid data race in cache #1650
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…n cache Signed-off-by: Joe Lanford <joe.lanford@gmail.com>
k8s-ci-robot added cncf-cla: yes k8s-ci-robot added the approved 
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What exactly races there? |
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With just the added test, the race detector shows this: Race detector details
TL;DR: it's multiple goroutines (one from each controller) trying to call SetGroupVersionKind on the same underlying object concurrently. |
alvaroaleman approved these changes Sep 2, 2021
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| [APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: alvaroaleman, joelanford The full list of commands accepted by this bot can be found here. The pull request process is described here Needs approval from an approver in each of these files:
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k8s-ci-robot added the lgtm 
vincepri reviewed Sep 2, 2021
Comment on lines +419 to +447
| func newGVKFixupWatcher(gvk schema.GroupVersionKind, watcher watch.Interface) watch.Interface { | ||
| ch := make(chan watch.Event) | ||
| w := &gvkFixupWatcher{ | ||
| gvk: gvk, | ||
| watcher: watcher, | ||
| ch: ch, | ||
| } | ||
| w.wg.Add(1) | ||
| go w.run() | ||
| return w | ||
| } | ||
| | ||
| func (w *gvkFixupWatcher) run() { | ||
| for e := range w.watcher.ResultChan() { | ||
| e.Object.GetObjectKind().SetGroupVersionKind(w.gvk) | ||
| w.ch <- e | ||
| } | ||
| w.wg.Done() | ||
| } | ||
| | ||
| func (w *gvkFixupWatcher) Stop() { | ||
| w.watcher.Stop() | ||
| w.wg.Wait() | ||
| close(w.ch) | ||
| } | ||
| | ||
| func (w *gvkFixupWatcher) ResultChan() <-chan watch.Event { | ||
| return w.ch | ||
| } |
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Is this the only way we can fix this behavior? Having an extra reader seems a bit overkill, given that's a reader on a reader, but I also don't have other options that I can think about.
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When multiple controllers are watching the same resource type with a metadata-only informer, a data race occurs in
sigs.k8s.io/controller-runtime/pkg/cache/internal.(*handlerPreserveGVK).resetGroupVersionKind()This data race is resolved by setting the GVK before the objects are written to the cache.
Signed-off-by: Joe Lanford joe.lanford@gmail.com