Merge pull request #3277 from guettli/syncPeriod-docs--sync-between-local-cache-and-reconciler-not-apiserver

📖 Docs for SyncPeriod: No sync from api-server.

Author: k8s-ci-robot

pkg/cache/cache.go

@@ -173,16 +173,14 @@ type Options struct {
 // recommend the `Reconcile` function return `reconcile.Result{RequeueAfter: t}`,
 // instead of `reconcile.Result{}`.
 //
-// SyncPeriod will trigger update events with the old object being equal to the new
-// object, except when the cache was out of sync.
-// If you filter update events like this:
-// Controller.Watch(
-// &source.Kind{Type: v1.MyCustomKind},
-// &handler.EnqueueRequestForObject{},
-// predicate.Or(predicate.GenerationChangedPredicate{},
-// predicate.LabelChangedPredicate{}))
-// then the SyncPeriod will not trigger a Reconcile call, because the update event
-// will be ignored by the predicate.
+// SyncPeriod will locally trigger an artificial Update event with the same
+// object in both ObjectOld and ObjectNew for everything that is in the
+// cache.
+//
+// Predicates or Handlers that expect ObjectOld and ObjectNew to be different
+// (such as GenerationChangedPredicate) will filter out this event, preventing
+// it from triggering a reconciliation.
+// SyncPeriod does not sync between the local cache and the server.
 SyncPeriod *time.Duration
 
 // ReaderFailOnMissingInformer configures the cache to return a ErrResourceNotCached error when a user