server: use "read-only" Gossip for tenants

We were previously using the Gossip instance of the TestServer against
which the tenant was initialized.

This commit trims the dependency further by initializing its own Gossip
instance which is never written to (i.e. `AddInfo` is never called) and
which does not accept incoming connections.

As a reminder, the remaining problematic uses of Gossip as of this
commit are:

- making a `nodeDialer` (for `DistSender`), tracked in:
  cockroachdb#47909
- access to the system config:
  - `(schemaChangeGCResumer).Resume`, tracked:
    cockroachdb#49691
  - `database.Cache`, tracked:
    cockroachdb#49692
- `(physicalplan).spanResolver` (for replica oracle).
  This is likely not a blocker as we can use a "dumber" oracle in this case;
  the oracle is used for distsql physical planning of which tenants will
  do none. Tracked in: cockroachdb#48432

Release note: None

pkg/gossip/gossip.go

@@ -1659,6 +1659,12 @@ type DeprecatedGossip struct {
 	w errorutil.TenantSQLDeprecatedWrapper
 }
 
+// Start calls .Start() on the underlying Gossip instance, which is assumed to
+// be non-nil.
+func (dg DeprecatedGossip) Start(advertAddr net.Addr, resolvers []resolver.Resolver) {
+	dg.w.Deprecated(0).(*Gossip).Start(advertAddr, resolvers)
+}
+
 // deprecated trades a Github issue tracking the removal of the call for the
 // wrapped Gossip instance.
 func (dg DeprecatedGossip) deprecated(issueNo int) *Gossip {

pkg/server/testserver.go

@@ -27,6 +27,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/config"
 	"github.com/cockroachdb/cockroach/pkg/config/zonepb"
 	"github.com/cockroachdb/cockroach/pkg/gossip"
+	"github.com/cockroachdb/cockroach/pkg/gossip/resolver"
 	"github.com/cockroachdb/cockroach/pkg/jobs"
 	"github.com/cockroachdb/cockroach/pkg/keys"
 	"github.com/cockroachdb/cockroach/pkg/kv"
@@ -437,27 +438,22 @@ func (d dummyProtectedTSProvider) Protect(context.Context, *kv.Txn, *ptpb.Record
 //  this is tracked in https://github.com/cockroachdb/cockroach/issues/47892.
 const fakeNodeID = roachpb.NodeID(1)
 
-func testSQLServerArgs(ts *TestServer, tenID roachpb.TenantID) sqlServerArgs {
-	stopper := ts.Stopper()
-	clusterName := ts.Cfg.ClusterName
-	// If we used a dummy gossip, DistSQL and random other things won't work.
-	// Just use the test server's for now.
-	//
-	// TODO(tbg): drop the Gossip dependency.
-	g := ts.Gossip()
-	ts = nil // prevent usage below
+func testSQLServerArgs(
+	stopper *stop.Stopper, kvClusterName string, tenID roachpb.TenantID,
+) sqlServerArgs {
 
 	st := cluster.MakeTestingClusterSettings()
 
 	sqlCfg := makeTestSQLConfig(st, tenID)
 
 	baseCfg := makeTestBaseConfig(st)
+	baseCfg.AmbientCtx.AddLogTag("sql", nil)
 	// TODO(tbg): this is needed so that the RPC heartbeats between the testcluster
 	// and this tenant work.
 	//
 	// TODO(tbg): address this when we introduce the real tenant RPCs in:
 	// https://github.com/cockroachdb/cockroach/issues/47898
-	baseCfg.ClusterName = clusterName
+	baseCfg.ClusterName = kvClusterName
 
 	clock := hlc.NewClock(hlc.UnixNano, time.Duration(baseCfg.MaxOffset))
 
@@ -474,13 +470,41 @@ func testSQLServerArgs(ts *TestServer, tenID roachpb.TenantID) sqlServerArgs {
 		rpcTestingKnobs,
 	)
 
+	// TODO(tbg): expose this registry via prometheus. See:
+	// https://github.com/cockroachdb/cockroach/issues/47905
+	registry := metric.NewRegistry()
+
 	var dsKnobs kvcoord.ClientTestingKnobs
 	if dsKnobsP, ok := baseCfg.TestingKnobs.DistSQL.(*kvcoord.ClientTestingKnobs); ok {
 		dsKnobs = *dsKnobsP
 	}
 	rpcRetryOptions := base.DefaultRetryOptions()
-	resolver := gossip.AddressResolver(g) // TODO(tbg): break gossip dep
-	nodeDialer := nodedialer.New(rpcContext, resolver)
+
+	// TODO(nvb): this use of Gossip needs to go. Tracked in:
+	// https://github.com/cockroachdb/cockroach/issues/47909
+	var g *gossip.Gossip
+	{
+		var nodeID base.NodeIDContainer
+		nodeID.Set(context.Background(), fakeNodeID)
+		var clusterID base.ClusterIDContainer
+		dummyGossipGRPC := rpc.NewServer(rpcContext) // never Serve()s anything
+		g = gossip.New(
+			baseCfg.AmbientCtx,
+			&clusterID,
+			&nodeID,
+			rpcContext,
+			dummyGossipGRPC,
+			stopper,
+			registry,
+			baseCfg.Locality,
+			&baseCfg.DefaultZoneConfig,
+		)
+	}
+
+	nodeDialer := nodedialer.New(
+		rpcContext,
+		gossip.AddressResolver(g), // TODO(nvb): break gossip dep
+	)
 	dsCfg := kvcoord.DistSenderConfig{
 		AmbientCtx:        baseCfg.AmbientCtx,
 		Settings:          st,
@@ -497,9 +521,7 @@ func testSQLServerArgs(ts *TestServer, tenID roachpb.TenantID) sqlServerArgs {
 	if p, ok := baseCfg.TestingKnobs.KVClient.(*kvcoord.ClientTestingKnobs); ok {
 		clientKnobs = *p
 	}
-	// TODO(tbg): expose this registry via prometheus. See:
-	// https://github.com/cockroachdb/cockroach/issues/47905
-	registry := metric.NewRegistry()
+
 	txnMetrics := kvcoord.MakeTxnMetrics(baseCfg.HistogramWindowInterval())
 	registry.AddMetricStruct(txnMetrics)
 	tcsFactory := kvcoord.NewTxnCoordSenderFactory(
@@ -594,13 +616,24 @@ func (ts *TestServer) StartTenant(params base.TestTenantArgs) (pgAddr string, _
 		return "", err
 	}
 
-	args := testSQLServerArgs(ts, params.TenantID)
-	if params.AllowSettingClusterSettings {
+	return startTenant(ts.Stopper(), ts.Cfg.ClusterName, ts.RPCAddr(), params.TenantID, params.AllowSettingClusterSettings)
+}
+
+func startTenant(
+	stopper *stop.Stopper,
+	kvClusterName string,
+	tsRPCAddr string,
+	tenID roachpb.TenantID,
+	allowSetClusterSetting bool,
+) (pgAddr string, _ error) {
+	args := testSQLServerArgs(stopper, kvClusterName, tenID)
+	// TODO(tbg): clean this up.
+	if allowSetClusterSetting {
 		args.TestingKnobs.TenantTestingKnobs = &sql.TenantTestingKnobs{
 			ClusterSettingsUpdater: args.Settings.MakeUpdater(),
 		}
 	}
-	ts = nil // proves we're not using it below
+	ctx := context.Background()
 
 	s, err := newSQLServer(ctx, args)
 	if err != nil {
@@ -639,6 +672,16 @@ func (ts *TestServer) StartTenant(params base.TestTenantArgs) (pgAddr string, _
 	)
 	orphanedLeasesTimeThresholdNanos := args.clock.Now().WallTime
 
+	{
+		rsvlr, err := resolver.NewResolver(tsRPCAddr)
+		if err != nil {
+			return "", err
+		}
+		// NB: gossip server is not bound to any address, so the advertise addr does
+		// not matter.
+		args.gossip.Start(pgL.Addr(), []resolver.Resolver{rsvlr})
+	}
+
 	if err := s.start(ctx,
 		args.stopper,
 		args.TestingKnobs,