Add drain delay flag

This flag allows to specify a period of time for which drainer should
wait after cordoning a node. This ensure that for example after instance
refresh pods don't become 'Pending' for some period of time waiting for
the new node to come up.

cmd/kubedrainer/main.go

@@ -112,6 +112,7 @@ func drainerFlags(options *drainer.Options) *pflag.FlagSet {
 	flags.Duration("timeout", options.Timeout, "The length of time to wait before giving up, zero means infinite")
 	flags.StringP("selector", "l", options.Selector, "Selector (label query) to filter on")
 	flags.StringP("pod-selector", "", options.PodSelector, "Label selector to filter pods on the node")
+	flags.String("drain-delay", options.DrainDelay.String(), "For how long to wait before draining a node")
 	return flags
 }
 

cmd/kubedrainer/serve.go

@@ -45,6 +45,7 @@ func serveCmd() *cobra.Command {
 			Timeout:             60 * time.Second,
 			DeleteLocalData:     true,
 			IgnoreAllDaemonSets: true,
+			DrainDelay:          0 * time.Second,
 		},
 		AWS: &autoscaling.Options{
 			LoopSleepTime: 10 * time.Second,

pkg/drainer/drainer.go

@@ -39,6 +39,7 @@ type Options struct {
 	DeleteLocalData     bool
 	Selector            string
 	PodSelector         string
+	DrainDelay          time.Duration `mapstructure:"drain-delay"`
 }
 
 func (o *Options) String() string {
@@ -72,6 +73,7 @@ func New(client kubernetes.Interface, options *Options) Drainer {
 			ErrOut: errOut,
 			Out:    out,
 		},
+		drainDelay: options.DrainDelay,
 		drainer: &drain.Helper{
 			Client:              client,
 			ErrOut:              errOut,
@@ -142,6 +144,9 @@ func (o *drainCmdOptions) Drain(nodeName string) error {
 		_ = printObj(n, o.Out)
 	}
 
+	log.Info().Msgf("Sleep for %v before starting to evict", o.drainDelay.String())
+	time.Sleep(o.drainDelay)
+
 	return o.deleteOrEvictPodsSimple(nodeName)
 }
 
@@ -151,6 +156,8 @@ type drainCmdOptions struct {
 	PrintFlags *genericclioptions.PrintFlags
 	ToPrinter  func(string) (printers.ResourcePrinterFunc, error)
 
+	drainDelay time.Duration
+
 	drainer *drain.Helper
 	nodes   *node.Node