testserver: add ShareMostTestingKnobsWithTenant option

The new ShareMostTestingKnobs copies nearly all of the testing knobs
specified for a TestServer to any tenant started for that server.

The goal here is to make it easier to write tests that depend on
testing hooks that work under probabilistic tenant testing.

Release justification: non-production code change

Release note: None

pkg/base/test_server_args.go

@@ -157,6 +157,12 @@ type TestServerArgs struct {
 	// or if some of the functionality being tested is not accessible from
 	// within tenants.
 	DisableDefaultTestTenant bool
+
+	// ShareMostTestingKnobsWithTenant should be set by tests that want their
+	// testing knobs shared with the any DefaultTestTenant that the server starts.
+	// See (*testserver).TestingKnobsForTenant for details on which knobs aren't
+	// shared.
+	ShareMostTestingKnobsWithTenant bool
 }
 
 // TestClusterArgs contains the parameters one can set when creating a test

pkg/server/testserver.go

@@ -496,6 +496,17 @@ func (ts *TestServer) TestingKnobs() *base.TestingKnobs {
 	return nil
 }
 
+// TestingKnobsForTenant returns a TestingKnobs that is used when starting Test
+// Tenants. These knobs are a copy of the Server's TestingKnobs with any knobs
+// that have been found to be problematic to share by default removed.
+func (ts *TestServer) TestingKnobsForTenant() base.TestingKnobs {
+	knobs := *ts.TestingKnobs()
+	// TODO(ssd): We don't share the Server knobs the testcluster setup code
+	// installed an RPC listener that is inappropriate for the tenant.
+	knobs.Server = nil
+	return knobs
+}
+
 // TenantStatusServer returns the TenantStatusServer used by the TestServer.
 func (ts *TestServer) TenantStatusServer() interface{} {
 	return ts.status
@@ -546,10 +557,14 @@ func (ts *TestServer) maybeStartDefaultTestTenant(ctx context.Context) error {
 		UseDatabase:                 ts.params.UseDatabase,
 		SSLCertsDir:                 ts.params.SSLCertsDir,
 		AllowSettingClusterSettings: true,
+	}
+	if ts.params.ShareMostTestingKnobsWithTenant {
+		params.TestingKnobs = ts.TestingKnobsForTenant()
+	} else {
 		// These settings are inherited from the SQL server creation in
 		// logicTest.newCluster, and are required to run the logic test suite
 		// successfully.
-		TestingKnobs: base.TestingKnobs{
+		params.TestingKnobs = base.TestingKnobs{
 			SQLExecutor: &sql.ExecutorTestingKnobs{
 				DeterministicExplain:            true,
 				UseTransactionalDescIDGenerator: useTransactionalDescIDGenerator,
@@ -558,7 +573,7 @@ func (ts *TestServer) maybeStartDefaultTestTenant(ctx context.Context) error {
 				AOSTClause: "AS OF SYSTEM TIME '-1us'",
 			},
 			RangeFeed: ts.TestingKnobs().RangeFeed,
-		},
+		}
 	}
 
 	tenant, err := ts.StartTenant(ctx, params)