Add disabling resync on controllers

CHANGELOG.md

@@ -18,6 +18,7 @@ NOTE: Breaking release in controllers.
 - Refactor metrics recorder implementation including the prometheus backend.
 - Refactor internal controller queue into a decorator implementation approach.
 - Remove `Delete` method from `controller.Handler` and simplify to only `Handle` method
+- Add `DisableResync` flag on controller configuration to disable the resync of all resources.
 
 ## [0.8.0] - 2019-12-11
 

README.md

@@ -161,6 +161,8 @@ The solution to this problems embraces simplicity once again, and mainly is to c
 - One of the type retrieval fails, the other type controller continues working (running in degradation mode).
 - Flexibility, e.g leader election for the primary type, no leader election for the secondary type.
 
+Controller config has a handy flag to disable resync (`DisableResync`), sometimes this can be useful on secondary resources.
+
 ## Compatibility matrix
 
 |             | Kubernetes <=1.9 | Kubernetes 1.10 | Kubernetes 1.11 | Kubernetes 1.12 | Kubernetes 1.13 | Kubernetes 1.14 |

controller/controller.go

@@ -53,6 +53,10 @@ type Config struct {
 	ResyncInterval time.Duration
 	// ProcessingJobRetries is the number of times the job will try to reprocess the event before returning a real error.
 	ProcessingJobRetries int
+	// DisableResync will disable resyncing, if disabled the controller only will react on event updates and resync
+	// all when it runs for the first time.
+	// This is useful for secondary resource controllers (e.g pod controller of a primary controller based on deployments).
+	DisableResync bool
 }
 
 func (c *Config) setDefaults() error {
@@ -90,6 +94,10 @@ func (c *Config) setDefaults() error {
 		c.ResyncInterval = 3 * time.Minute
 	}
 
+	if c.DisableResync {
+		c.ResyncInterval = 0 // 0 == resync disabled.
+	}
+
 	if c.ProcessingJobRetries < 0 {
 		c.ProcessingJobRetries = 0
 	}
@@ -149,7 +157,7 @@ func New(cfg *Config) (Controller, error) {
 	informer := cache.NewSharedIndexInformer(lw, nil, cfg.ResyncInterval, store)
 
 	// Set up our informer event handler.
-	// Objects are already in our local store. Add only keys/jobs on the queue so they can bre processed
+	// Objects are already in our local store. Add only keys/jobs on the queue so they can re processed
 	// afterwards.
 	informer.AddEventHandlerWithResyncPeriod(cache.ResourceEventHandlerFuncs{
 		AddFunc: func(obj interface{}) {

examples/controller-concurrency-handling/main.go

@@ -30,6 +30,7 @@ var (
 	sleepMS           int
 	intervalS         int
 	retries           int
+	disableResync     bool
 )
 
 func initFlags() error {
@@ -38,27 +39,13 @@ func initFlags() error {
 	fg.IntVar(&sleepMS, "sleep-ms", 25, "The number of milliseconds to sleep on each event handling")
 	fg.IntVar(&intervalS, "interval-s", 45, "The number of seconds to for reconciliation loop intervals")
 	fg.IntVar(&retries, "retries", 3, "The number of retries in case of error")
+	fg.BoolVar(&disableResync, "disable-resync", false, "Disables the resync")
 
 	err := fg.Parse(os.Args[1:])
 	if err != nil {
 		return err
 	}
 
-	if concurrentWorkers < 1 {
-		concurrentWorkers = 1
-	}
-
-	if sleepMS < 1 {
-		sleepMS = 25
-	}
-
-	if intervalS < 1 {
-		intervalS = 300
-	}
-	if retries < 0 {
-		retries = 0
-	}
-
 	return nil
 }
 
@@ -119,6 +106,7 @@ func run() error {
 		ProcessingJobRetries: retries,
 		ResyncInterval:       time.Duration(intervalS) * time.Second,
 		ConcurrentWorkers:    concurrentWorkers,
+		DisableResync:        disableResync,
 	}
 	ctrl, err := controller.New(cfg)
 	if err != nil {