session: prepare now prepares on all nodes

Fixes #249

session.go

@@ -3,6 +3,7 @@ package scylla
 import (
 	"fmt"
 	"log"
+	"sync"
 
 	"github.com/mmatczuk/scylla-go-driver/frame"
 	"github.com/mmatczuk/scylla-go-driver/transport"
@@ -147,24 +148,38 @@ func (s *Session) Query(content string) Query {
 }
 
 func (s *Session) Prepare(content string) (Query, error) {
-	n := s.policy.Node(s.cluster.NewQueryInfo(), 0)
-	conn := n.LeastBusyConn()
-	if conn == nil {
-		return Query{}, errNoConnection
-	}
-
 	stmt := transport.Statement{Content: content, Consistency: frame.ALL}
-	res, err := conn.Prepare(stmt)
 
-	return Query{session: s,
-		stmt: res,
-		exec: func(conn *transport.Conn, stmt transport.Statement, pagingState frame.Bytes) (transport.QueryResult, error) {
-			return conn.Execute(stmt, pagingState)
-		},
-		asyncExec: func(conn *transport.Conn, stmt transport.Statement, pagingState frame.Bytes, handler transport.ResponseHandler) {
-			conn.AsyncExecute(stmt, pagingState, handler)
-		},
-	}, err
+	// Prepare on all nodes concurrently.
+	nodes := s.cluster.Topology().Nodes
+	resStmt := make([]transport.Statement, len(nodes))
+	resErr := make([]error, len(nodes))
+	var wg sync.WaitGroup
+	for i := range nodes {
+		wg.Add(1)
+		go func(idx int) {
+			defer wg.Done()
+			resStmt[idx], resErr[idx] = nodes[idx].Prepare(stmt)
+		}(i)
+	}
+	wg.Wait()
+
+	// Find first result that succeeded.
+	for i := range nodes {
+		if resErr[i] == nil {
+			return Query{session: s,
+				stmt: resStmt[i],
+				exec: func(conn *transport.Conn, stmt transport.Statement, pagingState frame.Bytes) (transport.QueryResult, error) {
+					return conn.Execute(stmt, pagingState)
+				},
+				asyncExec: func(conn *transport.Conn, stmt transport.Statement, pagingState frame.Bytes, handler transport.ResponseHandler) {
+					conn.AsyncExecute(stmt, pagingState, handler)
+				},
+			}, nil
+		}
+	}
+
+	return Query{}, fmt.Errorf("prepare failed on all nodes, details: %v", resErr)
 }
 
 func (s *Session) NewTokenAwarePolicy() transport.HostSelectionPolicy {

session_integration_test.go

@@ -8,6 +8,7 @@ import (
 	"errors"
 	"io/ioutil"
 	"testing"
+	"time"
 
 	"go.uber.org/goleak"
 )
@@ -338,3 +339,41 @@ func TestTLSIntegration(t *testing.T) {
 		})
 	}
 }
+
+func TestPrepare(t *testing.T) {
+	defer goleak.VerifyNone(t)
+
+	cfg := DefaultSessionConfig("ks", "192.168.100.100:9042")
+	session, err := NewSession(cfg)
+
+	if err != nil {
+		panic(err)
+	}
+
+	defer session.Close()
+	initStmts := []string{
+		"DROP KEYSPACE IF EXISTS testks",
+		"CREATE KEYSPACE IF NOT EXISTS testks WITH replication = {'class': 'SimpleStrategy', 'replication_factor' : 1}",
+		"CREATE TABLE IF NOT EXISTS testks.doubles (pk bigint PRIMARY KEY, v bigint)",
+	}
+
+	for _, stmt := range initStmts {
+		q := session.Query(stmt)
+		if _, err := q.Exec(); err != nil {
+			t.Fatal(err)
+		}
+		time.Sleep(time.Second)
+	}
+
+	q, err := session.Prepare("INSERT INTO testks.doubles (pk, v) VALUES (?, ?)")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for i := int64(0); i < 1000; i++ {
+		_, err := q.BindInt64(0, i).BindInt64(1, 2*i).Exec()
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}

transport/cluster.go

@@ -41,7 +41,7 @@ type topology struct {
 	localDC    string
 	peers      peerMap
 	dcRacks    dcRacksMap
-	nodes      []*Node
+	Nodes      []*Node
 	policyInfo policyInfo
 	keyspaces  ksMap
 }
@@ -219,7 +219,7 @@ func (c *Cluster) refreshTopology() error {
 		// Every encountered node becomes known host for future use.
 		c.knownHosts[n.addr] = struct{}{}
 		t.peers[n.addr] = n
-		t.nodes = append(t.nodes, n)
+		t.Nodes = append(t.Nodes, n)
 		u[uniqueRack{dc: n.datacenter, rack: n.rack}] = struct{}{}
 		if err := parseTokensFromRow(n, r, &t.policyInfo.ring); err != nil {
 			return err
@@ -251,7 +251,7 @@ func newTopology() *topology {
 	return &topology{
 		peers:   make(peerMap),
 		dcRacks: make(dcRacksMap),
-		nodes:   make([]*Node, 0),
+		Nodes:   make([]*Node, 0),
 		policyInfo: policyInfo{
 			ring: make(Ring, 0),
 		},

transport/node.go

@@ -37,6 +37,10 @@ func (n *Node) Conn(token Token) *Conn {
 	return n.pool.Conn(token)
 }
 
+func (n *Node) Prepare(stmt Statement) (Statement, error) {
+	return n.LeastBusyConn().Prepare(stmt)
+}
+
 type RingEntry struct {
 	node           *Node
 	token          Token

transport/policy.go

@@ -86,7 +86,7 @@ func (pi *policyInfo) Preprocess(t *topology, ks keyspace) {
 }
 
 func (pi *policyInfo) preprocessSimpleStrategy(t *topology, stg strategy) {
-	pi.localNodes = t.nodes
+	pi.localNodes = t.Nodes
 	sort.Sort(pi.ring)
 	trie := trieRoot()
 	for i := range pi.ring {
@@ -122,14 +122,14 @@ func (pi *policyInfo) preprocessSimpleStrategy(t *topology, stg strategy) {
 }
 
 func (pi *policyInfo) preprocessRoundRobinStrategy(t *topology) {
-	pi.localNodes = t.nodes
+	pi.localNodes = t.Nodes
 	pi.remoteNodes = nil
 }
 
 func (pi *policyInfo) preprocessDCAwareRoundRobinStrategy(t *topology) {
 	pi.localNodes = make([]*Node, 0)
 	pi.remoteNodes = make([]*Node, 0)
-	for _, v := range t.nodes {
+	for _, v := range t.Nodes {
 		if v.datacenter == t.localDC {
 			pi.localNodes = append(pi.localNodes, v)
 		} else {