roachtest: don't specify virtual cluster in debug zips

Previously, we were always passing the system tenant when
taking debug zips in case a roachtest had overriden the
default virtual cluster. However, the debug zip command
already attempts to fetch all virtual clusters by passing
the --ccluster flag for each tenant. This behavior was suppresed
due to our hard coding of the system tenant, causing all debug
zips to be of the system tenant.

This changes it to instead pass nothing so the url has no
existing --ccluster flag.

Author: DarrylWong

pkg/cmd/roachtest/cluster.go

@@ -1389,12 +1389,14 @@ func (c *clusterImpl) FetchDebugZip(
 		for _, node := range nodes {
 			pgURLOpts := roachprod.PGURLOptions{
 				// `cockroach debug zip` does not support non root authentication.
-				Auth: install.AuthRootCert,
-				// request the system tenant specifically in case the test
-				// changed the default virtual cluster.
-				VirtualClusterName: install.SystemInterfaceName,
+				Auth:   install.AuthRootCert,
+				Secure: c.IsSecure(),
 			}
-			nodePgUrl, err := c.InternalPGUrl(ctx, l, c.Node(node), pgURLOpts)
+			// Use roachprod.PgURL directly as we want to bypass the default virtual cluster
+			// logic. The debug zip command already handles fetching all virtual clusters by passing
+			// the --ccluster for each tenant. Attempting to pass a --ccluster here will override
+			// that behavior and cause all debug zips to be of the same tenant.
+			urls, err := roachprod.PgURL(ctx, l, c.MakeNodes(c.Node(node)), install.CockroachNodeCertsDir, pgURLOpts)
 			if err != nil {
 				l.Printf("cluster.FetchDebugZip failed to retrieve PGUrl on node %d: %v", node, err)
 				continue
@@ -1409,7 +1411,7 @@ func (c *clusterImpl) FetchDebugZip(
 			cmd := roachtestutil.NewCommand("%s debug zip", test.DefaultCockroachPath).
 				Option("include-range-info").
 				Flag("exclude-files", fmt.Sprintf("'%s'", excludeFiles)).
-				Flag("url", fmt.Sprintf("'%s'", nodePgUrl[0])).
+				Flag("url", urls[0]).
 				MaybeFlag(c.IsSecure(), "certs-dir", install.CockroachNodeCertsDir).
 				Arg(zipName).
 				String()

pkg/roachprod/roachprod.go

@@ -1173,6 +1173,12 @@ func PgURL(
 	if len(urls) != len(nodes) {
 		return nil, errors.Errorf("have nodes %v, but urls %v from ips %v", nodes, urls, ips)
 	}
+	// We should never return an empty list of URLs as roachprod clusters always have at least
+	// one node. However, many callers of this function directly index into the slice returned,
+	// so check just in case.
+	if len(urls) == 0 {
+		return nil, errors.Newf("have nodes %v, but no urls were found", nodes)
+	}
 	return urls, nil
 }