WIP: Attempt at cordon but no drain

README.md

@@ -84,3 +84,11 @@ draino_cordoned_nodes_total{result="failed"} 1
 draino_drained_nodes_total{result="succeeded"} 1
 draino_drained_nodes_total{result="failed"} 1
 ```
+
+## Modes
+
+### Dry Run
+Draino can be run in dry run mode using the `--dry-run` flag.
+
+### Cordon Only
+Draino can also optionally be run in a mode where the nodes are only cordoned, and not drained. This can be achieved by using the `--no-drain` flag

cmd/draino/draino.go

@@ -54,6 +54,8 @@ func main() {
 		drainBuffer      = app.Flag("drain-buffer", "Minimum time between starting each drain. Nodes are always cordoned immediately.").Default(kubernetes.DefaultDrainBuffer.String()).Duration()
 		nodeLabels       = app.Flag("node-label", "Only nodes with this label will be eligible for cordoning and draining. May be specified multiple times.").PlaceHolder("KEY=VALUE").StringMap()
 
+		drain = app.Flag("drain", "Drain the nodes").Default("true").Bool()
+
 		evictDaemonSetPods    = app.Flag("evict-daemonset-pods", "Evict pods that were created by an extant DaemonSet.").Bool()
 		evictLocalStoragePods = app.Flag("evict-emptydir-pods", "Evict pods with local storage, i.e. with emptyDir volumes.").Bool()
 		evictUnreplicatedPods = app.Flag("evict-unreplicated-pods", "Evict pods that were not created by a replication controller.").Bool()
@@ -121,6 +123,7 @@ func main() {
 		kubernetes.NewAPICordonDrainer(cs,
 			kubernetes.MaxGracePeriod(*maxGracePeriod),
 			kubernetes.EvictionHeadroom(*evictionHeadroom),
+			kubernetes.WithDrain(*drain),
 			kubernetes.WithPodFilter(kubernetes.NewPodFilters(pf...))),
 		kubernetes.NewEventRecorder(cs),
 		kubernetes.WithLogger(log),

internal/kubernetes/drainer.go

@@ -35,6 +35,8 @@ const (
 	DefaultEvictionOverhead time.Duration = 30 * time.Second
 
 	kindDaemonSet = "DaemonSet"
+
+	DefaultWithDrain = true
 )
 
 type errTimeout struct{}
@@ -89,6 +91,7 @@ type APICordonDrainer struct {
 
 	maxGracePeriod   time.Duration
 	evictionHeadroom time.Duration
+	withDrain        bool
 }
 
 // SuppliedCondition defines the condition will be watched.
@@ -126,6 +129,13 @@ func WithPodFilter(f PodFilterFunc) APICordonDrainerOption {
 	}
 }
 
+// WithDrain determines if we're actually going to drain nodes
+func WithDrain(b bool) APICordonDrainerOption {
+	return func(d *APICordonDrainer) {
+		d.withDrain = b
+	}
+}
+
 // NewAPICordonDrainer returns a CordonDrainer that cordons and drains nodes via
 // the Kubernetes API.
 func NewAPICordonDrainer(c kubernetes.Interface, ao ...APICordonDrainerOption) *APICordonDrainer {
@@ -134,6 +144,7 @@ func NewAPICordonDrainer(c kubernetes.Interface, ao ...APICordonDrainerOption) *
 		filter:           NewPodFilters(),
 		maxGracePeriod:   DefaultMaxGracePeriod,
 		evictionHeadroom: DefaultEvictionOverhead,
+		withDrain:        DefaultWithDrain,
 	}
 	for _, o := range ao {
 		o(d)
@@ -163,6 +174,12 @@ func (d *APICordonDrainer) Cordon(n *core.Node) error {
 
 // Drain the supplied node. Evicts the node of all but mirror and DaemonSet pods.
 func (d *APICordonDrainer) Drain(n *core.Node) error {
+
+  // Do nothing 
+  if !d.withDrain {
+    return nil
+  }
+
 	pods, err := d.getPods(n.GetName())
 	if err != nil {
 		return errors.Wrapf(err, "cannot get pods for node %s", n.GetName())