roachprod: make reset command operate on a subset

Previously, the reset command would reset all VMs in a cluster. For failure
injection we require this to be able to work on a subset of nodes.

This change makes the reset command operate on a subset of nodes.

Epic: None
Release note: None

Author: herkolategan

pkg/cmd/roachprod/cli/commands.go

@@ -199,15 +199,17 @@ Removing nodes from the middle of the cluster is not supported yet.
 }
 
 func (cr *commandRegistry) buildResetCmd() *cobra.Command {
-	return &cobra.Command{
+	resetCmd := &cobra.Command{
 		Use:   "reset <cluster>",
-		Short: "reset *all* VMs in a cluster",
-		Long:  `Reset a cloud VM.`,
+		Short: "reset VMs in a cluster",
+		Long:  `Reset cloud VMs in a cluster.`,
 		Args:  cobra.ExactArgs(1),
 		Run: wrap(func(cmd *cobra.Command, args []string) (retErr error) {
 			return roachprod.Reset(config.Logger, args[0])
 		}),
 	}
+	addHelpAboutNodes(resetCmd)
+	return resetCmd
 }
 
 func (cr *commandRegistry) buildDestroyCmd() *cobra.Command {

pkg/roachprod/install/cluster_synced.go

@@ -2725,3 +2725,20 @@ done <<< "$HOSTS_LIST"
 
 	return nil
 }
+
+// Reset resets VMs in a cluster.
+func (c *SyncedCluster) Reset(l *logger.Logger) error {
+	if c.IsLocal() {
+		return nil
+	}
+
+	nodes := c.TargetNodes()
+	targetVMs := make(vm.List, len(nodes))
+	for idx, node := range nodes {
+		targetVMs[idx] = c.VMs[node-1]
+	}
+
+	return vm.FanOut(targetVMs, func(p vm.Provider, vms vm.List) error {
+		return p.Reset(l, vms)
+	})
+}

pkg/roachprod/roachprod.go

@@ -626,24 +626,14 @@ func Stage(
 	return install.StageApplication(ctx, l, c, applicationName, version, os, vm.CPUArch(arch), dir)
 }
 
-// Reset resets all VMs in a cluster.
+// Reset resets VMs in a cluster.
 func Reset(l *logger.Logger, clusterName string) error {
-	if err := LoadClusters(); err != nil {
-		return err
-	}
-
-	if config.IsLocalClusterName(clusterName) {
-		return nil
-	}
-
-	c, err := getClusterFromCloud(l, clusterName)
+	c, err := GetClusterFromCache(l, clusterName)
 	if err != nil {
 		return err
 	}
 
-	return vm.FanOut(c.VMs, func(p vm.Provider, vms vm.List) error {
-		return p.Reset(l, vms)
-	})
+	return c.Reset(l)
 }
 
 // SetupSSH sets up the keys and host keys for the vms in the cluster.