implement PR feedback

pkg/ctl/delete/nodegroup.go

@@ -57,7 +57,7 @@ func deleteNodeGroupWithRunFunc(cmd *cmdutils.Cmd, runFunc func(cmd *cmdutils.Cm
 		fs.DurationVar(&maxGracePeriod, "max-grace-period", defaultMaxGracePeriod, "Maximum pods termination grace period")
 		defaultDisableEviction := false
 		fs.BoolVar(&disableEviction, "disable-eviction", defaultDisableEviction, "Force drain to use delete, even if eviction is supported. This will bypass checking PodDisruptionBudgets, use with caution.")
-		fs.IntVar(&parallel, "parallel", 5, "Number of nodes to drain in parallel. Max 25")
+		fs.IntVar(&parallel, "parallel", 1, "Number of nodes to drain in parallel. Max 25")
 
 		cmd.Wait = false
 		cmdutils.AddWaitFlag(fs, &cmd.Wait, "deletion of all resources")

pkg/ctl/drain/nodegroup.go

@@ -56,7 +56,7 @@ func drainNodeGroupWithRunFunc(cmd *cmdutils.Cmd, runFunc func(cmd *cmdutils.Cmd
 		fs.BoolVar(&disableEviction, "disable-eviction", defaultDisableEviction, "Force drain to use delete, even if eviction is supported. This will bypass checking PodDisruptionBudgets, use with caution.")
 		cmdutils.AddTimeoutFlag(fs, &cmd.ProviderConfig.WaitTimeout)
 		fs.DurationVar(&nodeDrainWaitPeriod, "node-drain-wait-period", 0, "Amount of time to wait between draining nodes in a nodegroup")
-		fs.IntVar(&parallel, "parallel", 5, "Number of nodes to drain in parallel. Max 25")
+		fs.IntVar(&parallel, "parallel", 1, "Number of nodes to drain in parallel. Max 25")
 	})
 
 	cmdutils.AddCommonFlagsForAWS(cmd.FlagSetGroup, &cmd.ProviderConfig, true)

pkg/drain/nodegroup.go

@@ -144,15 +144,11 @@ func (n *NodeGroupDrainer) Drain() error {
 			logger.Debug("already drained: %v", mapToList(drainedNodes.Items()))
 			logger.Debug("will drain: %v", newPendingNodes.List())
 			for i, node := range newPendingNodes.List() {
-				// scoped values for concurrency
-				i := i
-				node := node
-
 				if err := sem.Acquire(ctx, 1); err != nil {
 					logger.Critical("failed to claim sem: %w", err)
 				}
 
-				go func() {
+				go func(i int, node string) {
 					defer sem.Release(1)
 					logger.Debug("starting drain of node %s", node)
 					pending, err := n.evictPods(node)
@@ -167,12 +163,11 @@ func (n *NodeGroupDrainer) Drain() error {
 						drainedNodes.Set(node, nil)
 					}
 
-					// only wait if we're not on the last node of this iteration
-					if n.nodeDrainWaitPeriod > 0 && i < newPendingNodes.Len()-1 {
+					if n.nodeDrainWaitPeriod > 0 {
 						logger.Debug("waiting for %.0f seconds before draining next node", n.nodeDrainWaitPeriod.Seconds())
 						time.Sleep(n.nodeDrainWaitPeriod)
 					}
-				}()
+				}(i, node)
 			}
 		}
 	}