update internal controller for more clean code and metrics

Author: adohe

pkg/internal/controller/controller.go

@@ -154,10 +154,7 @@ func (c *Controller) Start(stop <-chan struct{}) error {
 	log.Info("Starting workers", "controller", c.Name, "worker count", c.MaxConcurrentReconciles)
 	for i := 0; i < c.MaxConcurrentReconciles; i++ {
 		// Process work items
-		go wait.Until(func() {
-			for c.processNextWorkItem() {
-			}
-		}, c.JitterPeriod, stop)
+		go wait.Until(c.worker, c.JitterPeriod, stop)
 	}
 
 	c.Started = true
@@ -168,30 +165,32 @@ func (c *Controller) Start(stop <-chan struct{}) error {
 	return nil
 }
 
+// worker runs a worker thread that just dequeues items, processes them, and marks them done.
+// It enforces that the reconcileHandler is never invoked concurrently with the same object.
+func (c *Controller) worker() {
+	for c.processNextWorkItem() {
+	}
+}
+
 // processNextWorkItem will read a single work item off the workqueue and
-// attempt to process it, by calling the syncHandler.
+// attempt to process it, by calling the reconcileHandler.
 func (c *Controller) processNextWorkItem() bool {
-	// This code copy-pasted from the sample-Controller.
+	obj, shutdown := c.Queue.Get()
+	if shutdown {
+		return false
+	}
+	defer c.Queue.Done(obj)
 
+	return c.reconcileHandler(obj)
+}
+
+func (c *Controller) reconcileHandler(obj interface{}) bool {
 	// Update metrics after processing each item
 	reconcileStartTS := time.Now()
 	defer func() {
 		c.updateMetrics(time.Now().Sub(reconcileStartTS))
 	}()
 
-	obj, shutdown := c.Queue.Get()
-	if shutdown {
-		// Stop working
-		return false
-	}
-
-	// We call Done here so the workqueue knows we have finished
-	// processing this item. We also must remember to call Forget if we
-	// do not want this work item being re-queued. For example, we do
-	// not call Forget if a transient error occurs, instead the item is
-	// put back on the workqueue and attempted again after a back-off
-	// period.
-	defer c.Queue.Done(obj)
 	var req reconcile.Request
 	var ok bool
 	if req, ok = obj.(reconcile.Request); !ok {
@@ -204,7 +203,6 @@ func (c *Controller) processNextWorkItem() bool {
 		// Return true, don't take a break
 		return true
 	}
-
 	// RunInformersAndControllers the syncHandler, passing it the namespace/Name string of the
 	// resource to be synced.
 	if result, err := c.Do.Reconcile(req); err != nil {