Enable starting/stopping controllers and their caches

Author: kevindelgado

pkg/cache/cache.go

@@ -58,6 +58,9 @@ type Informers interface {
 	// of the underlying object.
 	GetInformerForKind(ctx context.Context, gvk schema.GroupVersionKind) (Informer, error)
 
+	// Remove the informer for the given object.
+	Remove(obj runtime.Object) error
+
 	// Start runs all the informers known to this cache until the given channel is closed.
 	// It blocks.
 	Start(stopCh <-chan struct{}) error

pkg/cache/informertest/fake_cache.go

@@ -125,6 +125,11 @@ func (c *FakeInformers) Start(stopCh <-chan struct{}) error {
 	return c.Error
 }
 
+// Remove implements Cache
+func (c *FakeInformers) Remove(obj runtime.Object) error {
+	return c.Error
+}
+
 // IndexField implements Cache
 func (c *FakeInformers) IndexField(ctx context.Context, obj runtime.Object, field string, extractValue client.IndexerFunc) error {
 	return nil

pkg/cache/multi_namespace_cache.go

@@ -94,6 +94,15 @@ func (c *multiNamespaceCache) GetInformerForKind(ctx context.Context, gvk schema
 	return &multiNamespaceInformer{namespaceToInformer: informers}, nil
 }
 
+func (c *multiNamespaceCache) Remove(obj runtime.Object) error {
+	for _, cache := range c.namespaceToCache {
+		if err := cache.Remove(obj); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (c *multiNamespaceCache) Start(stopCh <-chan struct{}) error {
 	for ns, cache := range c.namespaceToCache {
 		go func(ns string, cache Cache) {

pkg/internal/controller/controller.go

@@ -72,6 +72,9 @@ type Controller struct {
 	// Started is true if the Controller has been Started
 	Started bool
 
+	// saveWatches indicates not to clear startWatches when the controller is stopped.
+	saveWatches bool
+
 	// TODO(community): Consider initializing a logger with the Controller Name as the tag
 
 	// startWatches maintains a list of sources, handlers, and predicates to start when the controller is started.
@@ -172,9 +175,15 @@ func (c *Controller) Start(stop <-chan struct{}) error {
 
 		// All the watches have been started, we can reset the local slice.
 		//
-		// We should never hold watches more than necessary, each watch source can hold a backing cache,
+		// We should usually hold watches more than necessary, each watch source can hold a backing cache,
 		// which won't be garbage collected if we hold a reference to it.
-		c.startWatches = nil
+
+		// The exception to this is when the saveWatches is set to true,
+		// meaning the controller is intending to run Start() again.
+		// In this case it needs to knowledge of the watches for when the controller is restarted.
+		if !c.saveWatches {
+			c.startWatches = nil
+		}
 
 		if c.JitterPeriod == 0 {
 			c.JitterPeriod = 1 * time.Second
@@ -293,3 +302,13 @@ func (c *Controller) InjectFunc(f inject.Func) error {
 func (c *Controller) updateMetrics(reconcileTime time.Duration) {
 	ctrlmetrics.ReconcileTime.WithLabelValues(c.Name).Observe(reconcileTime.Seconds())
 }
+
+// ResetStart sets Started to false to enable running Start on the controller again.
+func (c *Controller) ResetStart() {
+	c.Started = false
+}
+
+// SaveWatches indicates that watches should not be cleared when the controller is stopped.
+func (c *Controller) SaveWatches() {
+	c.saveWatches = true
+}