func acquire(
	s *server.TestServer, descID sqlbase.ID, version sqlbase.DescriptorVersion,
) (*csql.LeaseState, error) {
	var lease *csql.LeaseState
	err := s.DB().Txn(context.TODO(), func(txn *client.Txn) error {
		var err error
		lease, err = s.LeaseManager().(*csql.LeaseManager).Acquire(txn, descID, version)
		return err
	})
	return lease, err
}

// FindRangeLease is similar to FindRangeLeaseHolder but returns a Lease proto
// without verifying if the lease is still active. Instead, it returns a time-
// stamp taken off the queried node's clock.
func (tc *TestCluster) FindRangeLease(
	rangeDesc *roachpb.RangeDescriptor, hint *ReplicationTarget,
) (_ *roachpb.Lease, now hlc.Timestamp, _ error) {
	if hint != nil {
		var ok bool
		if _, ok = rangeDesc.GetReplicaDescriptor(hint.StoreID); !ok {
			return nil, hlc.ZeroTimestamp, errors.Errorf(
				"bad hint: %+v; store doesn't have a replica of the range", hint)
		}
	} else {
		hint = &ReplicationTarget{
			NodeID:  rangeDesc.Replicas[0].NodeID,
			StoreID: rangeDesc.Replicas[0].StoreID}
	}

	// Find the server indicated by the hint and send a LeaseInfoRequest through
	// it.
	var hintServer *server.TestServer
	for _, s := range tc.Servers {
		if s.GetNode().Descriptor.NodeID == hint.NodeID {
			hintServer = s
			break
		}
	}
	if hintServer == nil {
		return nil, hlc.ZeroTimestamp, errors.Errorf("bad hint: %+v; no such node", hint)
	}
	leaseReq := roachpb.LeaseInfoRequest{
		Span: roachpb.Span{
			Key: rangeDesc.StartKey.AsRawKey(),
		},
	}
	leaseResp, pErr := client.SendWrappedWith(
		context.TODO(),
		hintServer.DB().GetSender(),
		roachpb.Header{
			// INCONSISTENT read, since we want to make sure that the node used to
			// send this is the one that processes the command, for the hint to
			// matter.
			ReadConsistency: roachpb.INCONSISTENT,
		},
		&leaseReq)
	if pErr != nil {
		return nil, hlc.ZeroTimestamp, pErr.GoError()
	}
	return leaseResp.(*roachpb.LeaseInfoResponse).Lease, hintServer.Clock().Now(), nil
}

// splitRangeAtVal splits the range for a table with schema
// `CREATE TABLE test (k INT PRIMARY KEY)` at row with value pk (the row will be
// the first on the right of the split).
func splitRangeAtVal(
	ts *server.TestServer, tableDesc *sqlbase.TableDescriptor, pk int,
) (roachpb.RangeDescriptor, roachpb.RangeDescriptor, error) {
	if len(tableDesc.Indexes) != 0 {
		return roachpb.RangeDescriptor{}, roachpb.RangeDescriptor{},
			errors.Errorf("expected table with just a PK, got: %+v", tableDesc)
	}
	pik, err := sqlbase.MakePrimaryIndexKey(tableDesc, pk)
	if err != nil {
		return roachpb.RangeDescriptor{}, roachpb.RangeDescriptor{}, err
	}

	startKey := keys.MakeRowSentinelKey(pik)
	leftRange, rightRange, err := ts.SplitRange(startKey)
	if err != nil {
		return roachpb.RangeDescriptor{}, roachpb.RangeDescriptor{},
			errors.Wrapf(err, "failed to split at row: %d", pk)
	}
	return leftRange, rightRange, nil
}

func waitForConfigChange(t *testing.T, s *server.TestServer) config.SystemConfig {
	var foundDesc sqlbase.Descriptor
	var cfg config.SystemConfig
	testutils.SucceedsSoon(t, func() error {
		var ok bool
		if cfg, ok = s.Gossip().GetSystemConfig(); ok {
			if val := cfg.GetValue(configDescKey); val != nil {
				if err := val.GetProto(&foundDesc); err != nil {
					t.Fatal(err)
				}
				if id := foundDesc.GetDatabase().GetID(); id != configID {
					return errors.Errorf("expected database id %d; got %d", configID, id)
				}
				return nil
			}
		}
		return errors.Errorf("got nil system config")
	})
	return cfg
}

// forceNewConfig forces a system config update by writing a bogus descriptor with an
// incremented value inside. It then repeatedly fetches the gossip config until the
// just-written descriptor is found.
func forceNewConfig(t *testing.T, s *server.TestServer) config.SystemConfig {
	configID++
	configDesc := &sqlbase.Descriptor{
		Union: &sqlbase.Descriptor_Database{
			Database: &sqlbase.DatabaseDescriptor{
				Name:       "sentinel",
				ID:         configID,
				Privileges: &sqlbase.PrivilegeDescriptor{},
			},
		},
	}

	// This needs to be done in a transaction with the system trigger set.
	if err := s.DB().Txn(context.TODO(), func(txn *client.Txn) error {
		txn.SetSystemConfigTrigger()
		return txn.Put(configDescKey, configDesc)
	}); err != nil {
		t.Fatal(err)
	}
	return waitForConfigChange(t, s)
}