Merge cockroachdb#64703

64703: roachtest: fix multitenant-upgrade r=erikgrinaker a=tbg

The test failed for two reasons:

- it was hard-coding 20.2 in one place where it shouldn't have
- it implicitly assumes that PredecessorVersion(21.2) is a 21.1 release
  that has cockroachdb#60730, but that will only be true in a month or so (when we
  have 21.1.1). Without cockroachdb#60730, tenant 11 in the test will have no
  cluster version persisted and so things don't work well. Work around
  this by setting the cluster version explicitly. This isn't a
  production concern since we are not going to upgrade tenants without
  a cluster version into 21.2; they will either have been created by a
  21.1.1+ host cluster (and thus have a cluster version) or been
  migrated from a 20.2 deployment into a 21.1.1+ deployment, which also
  entails giving them a cluster version.

Fixes cockroachdb#64615.

Release note: None


Co-authored-by: Tobias Grieger <tobias.b.grieger@gmail.com>

pkg/cmd/roachtest/multitenant_upgrade.go

@@ -165,7 +165,13 @@ func runMultiTenantUpgrade(ctx context.Context, t *test, c *cluster, v version.V
 			withResults([][]string{{"1", "bar"}}))
 
 	t.Status("preserving downgrade option on host server")
-	runner.Exec(t, `SET CLUSTER SETTING cluster.preserve_downgrade_option = '20.2'`)
+	{
+		s := runner.QueryStr(t, `SHOW CLUSTER SETTING version`)
+		runner.Exec(
+			t,
+			`SET CLUSTER SETTING cluster.preserve_downgrade_option = $1`, s[0][0],
+		)
+	}
 
 	t.Status("upgrading host server")
 	c.Stop(ctx, kvNodes)
@@ -230,12 +236,29 @@ func runMultiTenantUpgrade(ctx context.Context, t *test, c *cluster, v version.V
 	t.Status("starting the tenant 11 server with the current binary")
 	tenant11.start(ctx, t, c, currentBinary)
 
+	if v, err := version.Parse("v" + predecessor); err != nil {
+		t.Fatal(err)
+	} else if !v.AtLeast(version.MustParse("v21.1.1")) {
+		// If we take this branch, the current branch is 21.2 but we haven't released 21.1.1 yet.
+		// The multi-tenant upgrade PR #60730 will only be contained in 21.1.1. That PR is responsible
+		// for giving tenants the initial cluster version, which is thus absent here. We still want to
+		// run this test until #60730 is backported, so fill the cluster version in. Without this, the
+		// tenant would report a cluster version of 20.2 which is going to trip up the test. We won't
+		// actually upgrade tenants in production in scenarios in which this branch is active (the host
+		// cluster will be at the latest patch release before attempting an upgrade, which is going to
+		// be at least 21.1.1).
+		// This can be deleted once the PredecessorVersion(21.2) is >= 21.1.1.
+		verifySQL(t, tenant11.pgURL, mkStmt(`SET CLUSTER SETTING version = $1`, initialVersion))
+	}
+
 	t.Status("verify tenant 11 server works with the new binary")
-	verifySQL(t, tenant11.pgURL,
-		mkStmt(`SELECT * FROM foo LIMIT 1`).
-			withResults([][]string{{"1", "bar"}}),
-		mkStmt("SHOW CLUSTER SETTING version").
-			withResults([][]string{{initialVersion}}))
+	{
+		verifySQL(t, tenant11.pgURL,
+			mkStmt(`SELECT * FROM foo LIMIT 1`).
+				withResults([][]string{{"1", "bar"}}),
+			mkStmt("SHOW CLUSTER SETTING version").
+				withResults([][]string{{initialVersion}}))
+	}
 
 	// Note that this is exercising a path we likely want to eliminate in the
 	// future where the tenant is upgraded before the KV nodes.