roachprod: fix roachprod init.

When a cluster is started with the `--skip-init` option, the caller
can run `roachprod init` at any time to initialize the
cluster. Unfortunately, the code used to initialize the cluster was
duplicated: one copy existed in the `start` path, and another in the
`init` path. Since the latter is used far less frequently, it had a
bug that went unnoticed: it hardcoded the first node index as `0`,
when node indices start at 1.

This commit fixes the issue by updating the constant and sharing code
between `init `and `start`.

Fixes #88226.

Release note: None

pkg/roachprod/install/cluster_synced.go

@@ -2290,12 +2290,11 @@ func (c *SyncedCluster) ParallelE(
 
 // Init initializes the cluster. It does it through node 1 (as per TargetNodes)
 // to maintain parity with auto-init behavior of `roachprod start` (when
-// --skip-init) is not specified. The implementation should be kept in
-// sync with Start().
+// --skip-init) is not specified.
 func (c *SyncedCluster) Init(ctx context.Context, l *logger.Logger) error {
 	// See Start(). We reserve a few special operations for the first node, so we
 	// strive to maintain the same here for interoperability.
-	const firstNodeIdx = 0
+	const firstNodeIdx = 1
 
 	l.Printf("%s: initializing cluster\n", c.Name)
 	initOut, err := c.initializeCluster(ctx, firstNodeIdx)

pkg/roachprod/install/cockroach.go

@@ -184,27 +184,9 @@ func (c *SyncedCluster) Start(ctx context.Context, l *logger.Logger, startOpts S
 
 		shouldInit := !c.useStartSingleNode()
 		if shouldInit {
-			l.Printf("%s: initializing cluster", c.Name)
-			initOut, err := c.initializeCluster(ctx, node)
-			if err != nil {
-				return nil, errors.WithDetail(err, "unable to initialize cluster")
+			if err := c.Init(ctx, l); err != nil {
+				return nil, errors.Wrap(err, "failed to initialize cluster")
 			}
-
-			if initOut != "" {
-				l.Printf(initOut)
-			}
-		}
-
-		// We're sure to set cluster settings after having initialized the
-		// cluster.
-
-		l.Printf("%s: setting cluster settings", c.Name)
-		clusterSettingsOut, err := c.setClusterSettings(ctx, l, node)
-		if err != nil {
-			return nil, errors.Wrap(err, "unable to set cluster settings")
-		}
-		if clusterSettingsOut != "" {
-			l.Printf(clusterSettingsOut)
 		}
 		return nil, nil
 	})