transport: cluster, add Nodes() in place of Topology() and setTopology()

The point of Topology() and setTopology() cluster methods was to give
some sort of type safety as topology was an atomic.Value that can hold
any type. As topology is now an atomic.Pointer they are no longer needed.

Session sometimes needs to perform a query on all nodes of
the cluster, to allow that cluster now has an exported Nodes() method.

session.go

@@ -161,7 +161,7 @@ func (s *Session) Prepare(ctx context.Context, content string) (Query, error) {
 	stmt := transport.Statement{Content: content, Consistency: frame.ALL}
 
 	// Prepare on all nodes concurrently.
-	nodes := s.cluster.Topology().Nodes
+	nodes := s.cluster.Nodes()
 	resStmt := make([]transport.Statement, len(nodes))
 	resErr := make([]error, len(nodes))
 	var wg sync.WaitGroup
@@ -234,7 +234,7 @@ func (s *Session) handleAutoAwaitSchemaAgreement(ctx context.Context, stmt strin
 
 func (s *Session) CheckSchemaAgreement(ctx context.Context) (bool, error) {
 	// Get schema version from all nodes concurrently.
-	nodes := s.cluster.Topology().Nodes
+	nodes := s.cluster.Nodes()
 	versions := make([]frame.UUID, len(nodes))
 	errors := make([]error, len(nodes))
 	var wg sync.WaitGroup

transport/cluster.go

@@ -38,6 +38,10 @@ type Cluster struct {
 	queryInfoCounter atomic.Uint64
 }
 
+func (c *Cluster) Nodes() []*Node {
+	return c.topology.Load().Nodes
+}
+
 type topology struct {
 	localDC    string
 	peers      peerMap
@@ -86,13 +90,13 @@ type QueryInfo struct {
 func (c *Cluster) NewQueryInfo() QueryInfo {
 	return QueryInfo{
 		tokenAware: false,
-		topology:   c.Topology(),
+		topology:   c.topology.Load(),
 		offset:     c.generateOffset(),
 	}
 }
 
 func (c *Cluster) NewTokenAwareQueryInfo(t Token, ks string) (QueryInfo, error) {
-	top := c.Topology()
+	top := c.topology.Load()
 	// When keyspace is not specified, we take default keyspace from ConnConfig.
 	if ks == "" {
 		if c.cfg.Keyspace == "" {
@@ -144,7 +148,7 @@ func NewCluster(ctx context.Context, cfg ConnConfig, p HostSelectionPolicy, e []
 	if p, ok := p.(*TokenAwarePolicy); ok {
 		localDC = p.localDC
 	}
-	c.setTopology(&topology{localDC: localDC})
+	c.topology.Store(&topology{localDC: localDC})
 
 	if control, err := c.NewControl(ctx); err != nil {
 		return nil, fmt.Errorf("create control connection: %w", err)
@@ -190,9 +194,9 @@ func (c *Cluster) refreshTopology(ctx context.Context) error {
 		return fmt.Errorf("query info about nodes in cluster: %w", err)
 	}
 
-	old := c.Topology().peers
+	old := c.topology.Load().peers
 	t := newTopology()
-	t.localDC = c.Topology().localDC
+	t.localDC = c.topology.Load().localDC
 	t.keyspaces, err = c.updateKeyspace(ctx)
 	if err != nil {
 		return fmt.Errorf("query keyspaces: %w", err)
@@ -247,7 +251,7 @@ func (c *Cluster) refreshTopology(ctx context.Context) error {
 		t.policyInfo.Preprocess(t, keyspace{})
 	}
 
-	c.setTopology(t)
+	c.topology.Store(t)
 	drainChan(c.refreshChan)
 	return nil
 }
@@ -442,14 +446,6 @@ func parseTokensFromRow(n *Node, r frame.Row, ring *Ring) error {
 	return nil
 }
 
-func (c *Cluster) Topology() *topology {
-	return c.topology.Load()
-}
-
-func (c *Cluster) setTopology(t *topology) {
-	c.topology.Store(t)
-}
-
 // handleEvent creates function which is passed to control connection
 // via registerEvents in order to handle events right away instead
 // of registering handlers for them.
@@ -478,7 +474,7 @@ func (c *Cluster) handleTopologyChange(v *TopologyChange) {
 
 func (c *Cluster) handleStatusChange(v *StatusChange) {
 	log.Printf("cluster: handle status change: %+#v", v)
-	m := c.Topology().peers
+	m := c.topology.Load().peers
 	addr := v.Address.String()
 	if n, ok := m[addr]; ok {
 		switch v.Status {
@@ -549,7 +545,7 @@ func (c *Cluster) tryReopenControl(ctx context.Context) {
 func (c *Cluster) handleClose() {
 	log.Printf("cluster: handle cluster close")
 	c.control.Close()
-	m := c.Topology().peers
+	m := c.topology.Load().peers
 	for _, v := range m {
 		if v.pool != nil {
 			v.pool.Close()

transport/cluster_integration_test.go

@@ -17,7 +17,7 @@ import (
 const awaitingChanges = 100 * time.Millisecond
 
 func compareNodes(c *Cluster, addr string, expected *Node) error {
-	m := c.Topology().peers
+	m := c.topology.Load().peers
 	got, ok := m[addr]
 	switch {
 	case !ok:
@@ -80,7 +80,7 @@ func TestClusterIntegration(t *testing.T) {
 	}
 
 	// There should be at least system keyspaces present.
-	if len(c.Topology().keyspaces) == 0 {
+	if len(c.topology.Load().keyspaces) == 0 {
 		t.Fatalf("Keyspaces failed to load")
 	}
 

transport/policy_test.go

@@ -33,7 +33,7 @@ func mockCluster(t *topology, ks, localDC string) *Cluster {
 	} else {
 		t.policyInfo.Preprocess(t, keyspace{})
 	}
-	c.setTopology(t)
+	c.topology.Store(t)
 
 	return &c
 }