Consolidate CreateSession into NewSession

CreateSession on the cluster config is a helper method to setup
defaults for the session, but it also does a lot of the setup, such
as creating the connection pool and creating the host discovery
goroutine.

Move all this logic into NewSession so that CreateSession now just
returns NewSession.

cluster.go

@@ -101,52 +101,7 @@ func NewCluster(hosts ...string) *ClusterConfig {
 // CreateSession initializes the cluster based on this config and returns a
 // session object that can be used to interact with the database.
 func (cfg *ClusterConfig) CreateSession() (*Session, error) {
-
-	//Check that hosts in the ClusterConfig is not empty
-	if len(cfg.Hosts) < 1 {
-		return nil, ErrNoHosts
-	}
-
-	maxStreams := 128
-	if cfg.ProtoVersion > protoVersion2 {
-		maxStreams = 32768
-	}
-
-	if cfg.NumStreams <= 0 || cfg.NumStreams > maxStreams {
-		cfg.NumStreams = maxStreams
-	}
-
-	pool, err := cfg.ConnPoolType(cfg)
-	if err != nil {
-		return nil, err
-	}
-
-	//Adjust the size of the prepared statements cache to match the latest configuration
-	stmtsLRU.Lock()
-	initStmtsLRU(cfg.MaxPreparedStmts)
-	stmtsLRU.Unlock()
-
-	//See if there are any connections in the pool
-	if pool.Size() > 0 {
-		s := NewSession(pool, *cfg)
-		s.SetConsistency(cfg.Consistency)
-		s.SetPageSize(cfg.PageSize)
-
-		if cfg.DiscoverHosts {
-			hostSource := &ringDescriber{
-				session:    s,
-				dcFilter:   cfg.Discovery.DcFilter,
-				rackFilter: cfg.Discovery.RackFilter,
-			}
-
-			go hostSource.run(cfg.Discovery.Sleep)
-		}
-
-		return s, nil
-	}
-
-	pool.Close()
-	return nil, ErrNoConnectionsStarted
+	return NewSession(*cfg)
 }
 
 var (

session.go

@@ -44,13 +44,61 @@ type Session struct {
 }
 
 // NewSession wraps an existing Node.
-func NewSession(p ConnectionPool, c ClusterConfig) *Session {
-	session := &Session{Pool: p, cons: c.Consistency, prefetch: 0.25, cfg: c}
+func NewSession(cfg ClusterConfig) (*Session, error) {
+	//Check that hosts in the ClusterConfig is not empty
+	if len(cfg.Hosts) < 1 {
+		return nil, ErrNoHosts
+	}
+
+	maxStreams := 128
+	if cfg.ProtoVersion > protoVersion2 {
+		maxStreams = 32768
+	}
+
+	if cfg.NumStreams <= 0 || cfg.NumStreams > maxStreams {
+		cfg.NumStreams = maxStreams
+	}
+
+	pool, err := cfg.ConnPoolType(&cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	//Adjust the size of the prepared statements cache to match the latest configuration
+	stmtsLRU.Lock()
+	initStmtsLRU(cfg.MaxPreparedStmts)
+	stmtsLRU.Unlock()
+
+	s := &Session{
+		Pool:     pool,
+		cons:     cfg.Consistency,
+		prefetch: 0.25,
+		cfg:      cfg,
+	}
+
+	//See if there are any connections in the pool
+	if pool.Size() > 0 {
+		s.routingKeyInfoCache.lru = lru.New(cfg.MaxRoutingKeyInfo)
+
+		s.SetConsistency(cfg.Consistency)
+		s.SetPageSize(cfg.PageSize)
+
+		if cfg.DiscoverHosts {
+			hostSource := &ringDescriber{
+				session:    s,
+				dcFilter:   cfg.Discovery.DcFilter,
+				rackFilter: cfg.Discovery.RackFilter,
+			}
+
+			go hostSource.run(cfg.Discovery.Sleep)
+		}
+
+		return s, nil
+	}
 
-	// create the query info cache
-	session.routingKeyInfoCache.lru = lru.New(c.MaxRoutingKeyInfo)
+	s.Close()
 
-	return session
+	return nil, ErrNoConnectionsStarted
 }
 
 // SetConsistency sets the default consistency level for this session. This

session_test.go

@@ -9,13 +9,18 @@ import (
 
 func TestSessionAPI(t *testing.T) {
 
-	cfg := ClusterConfig{}
-	pool, err := NewSimplePool(&cfg)
+	cfg := &ClusterConfig{}
+	pool, err := NewSimplePool(cfg)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	s := NewSession(pool, cfg)
+	s := &Session{
+		Pool: pool,
+		cfg:  *cfg,
+		cons: Quorum,
+	}
+
 	defer s.Close()
 
 	s.SetConsistency(All)
@@ -154,14 +159,13 @@ func TestQueryShouldPrepare(t *testing.T) {
 
 func TestBatchBasicAPI(t *testing.T) {
 
-	cfg := ClusterConfig{}
+	cfg := NewCluster("127.0.0.1")
 	cfg.RetryPolicy = &SimpleRetryPolicy{NumRetries: 2}
-	pool, err := NewSimplePool(&cfg)
+
+	s, err := cfg.CreateSession()
 	if err != nil {
 		t.Fatal(err)
 	}
-
-	s := NewSession(pool, cfg)
 	defer s.Close()
 
 	b := s.NewBatch(UnloggedBatch)