clusterStart: only run necessary actions

- e.g. can only wait for specific log messages, if the nodes have been
restarted for real and not if they were already running

fixes #847

pkg/client/cluster.go

@@ -848,6 +848,7 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 	var agents []*k3d.Node
 	var aux []*k3d.Node
 	for _, n := range cluster.Nodes {
+		if !n.State.Running {
 			if n.Role == k3d.ServerRole {
 				if n.ServerOpts.IsInit {
 					initNode = n
@@ -859,6 +860,9 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 			} else {
 				aux = append(aux, n)
 			}
+		} else {
+			l.Log().Tracef("Node %s already running.", n.Name)
+		}
 	}
 
 	// sort list of servers for properly ordered sequential start
@@ -884,6 +888,7 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 	/*
 	 * Server Nodes
 	 */
+	if len(servers) > 0 {
 		l.Log().Infoln("Starting servers...")
 		for _, serverNode := range servers {
 			if err := NodeStart(ctx, runtime, serverNode, &k3d.NodeStartOpts{
@@ -894,11 +899,14 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 				return fmt.Errorf("Failed to start server %s: %+v", serverNode.Name, err)
 			}
 		}
+	} else {
+		l.Log().Infoln("All servers already running.")
+	}
 
 	/*
 	 * Agent Nodes
 	 */
-
+	if len(agents) > 0 {
 		agentWG, aCtx := errgroup.WithContext(ctx)
 
 		l.Log().Infoln("Starting agents...")
@@ -915,11 +923,15 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 		if err := agentWG.Wait(); err != nil {
 			return fmt.Errorf("Failed to add one or more agents: %w", err)
 		}
+	} else {
+		l.Log().Infoln("All agents already running.")
+	}
 
 	/*
 	 * Auxiliary/Helper Nodes
 	 */
 
+	if len(aux) > 0 {
 		helperWG, hCtx := errgroup.WithContext(ctx)
 		l.Log().Infoln("Starting helpers...")
 		for _, helperNode := range aux {
@@ -941,11 +953,16 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 		if err := helperWG.Wait(); err != nil {
 			return fmt.Errorf("Failed to add one or more helper nodes: %w", err)
 		}
+	} else {
+		l.Log().Infoln("All helpers already running.")
+	}
 
 	/*
 	 * Additional Cluster Preparation (post start)
 	 */
 
+	if len(servers) > 0 || len(agents) > 0 { // TODO: make checks for required cluster start actions cleaner
+
 		postStartErrgrp, postStartErrgrpCtx := errgroup.WithContext(ctx)
 
 		/*** DNS ***/
@@ -955,6 +972,7 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 			return prepInjectHostIP(postStartErrgrpCtx, runtime, cluster, &clusterStartOpts)
 		})
 
+		if len(servers) > 0 {
 			postStartErrgrp.Go(func() error {
 
 				if cluster.Network.Name == "host" {
@@ -1021,10 +1039,12 @@ func ClusterStart(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clust
 				}
 				return nil
 			})
+		}
 
 		if err := postStartErrgrp.Wait(); err != nil {
 			return fmt.Errorf("error during post-start cluster preparation: %w", err)
 		}
+	}
 
 	return nil
 }