hbase-store: use a fixed conn pool instead of single connection

for better rpc performance

store/hbase/kv.go

@@ -16,8 +16,10 @@ package hbasekv
 import (
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/juju/errors"
+	"github.com/ngaut/log"
 	"github.com/pingcap/go-hbase"
 	"github.com/pingcap/go-themis"
 	"github.com/pingcap/tidb/kv"
@@ -30,6 +32,8 @@ const (
 	hbaseQualifier = "q"
 	// hbaseFmlAndQual is a shortcut.
 	hbaseFmlAndQual = hbaseColFamily + ":" + hbaseQualifier
+	// fix length conn pool
+	hbaseConnPoolSize = 10
 )
 
 var (
@@ -61,21 +65,24 @@ type hbaseStore struct {
 	mu        sync.Mutex
 	zkInfo    string
 	storeName string
-	cli       hbase.HBaseClient
+	conns     []hbase.HBaseClient
 }
 
 func (s *hbaseStore) Begin() (kv.Transaction, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
-
-	t := themis.NewTxn(s.cli)
+	// get random conn
+	hbaseCli := s.conns[time.Now().UnixNano()%hbaseConnPoolSize]
+	t := themis.NewTxn(hbaseCli)
 	txn := newHbaseTxn(t, s.storeName)
 	txn.UnionStore = kv.NewUnionStore(newHbaseSnapshot(t, s.storeName))
 	return txn, nil
 }
 
 func (s *hbaseStore) GetSnapshot(ver kv.Version) (kv.MvccSnapshot, error) {
-	t := themis.NewTxn(s.cli)
+	// get random conn
+	hbaseCli := s.conns[time.Now().UnixNano()%hbaseConnPoolSize]
+	t := themis.NewTxn(hbaseCli)
 	return newHbaseSnapshot(t, s.storeName), nil
 }
 
@@ -84,7 +91,16 @@ func (s *hbaseStore) Close() error {
 	defer mc.mu.Unlock()
 
 	delete(mc.cache, s.zkInfo)
-	return s.cli.Close()
+
+	var err error
+	for _, conn := range s.conns {
+		err = conn.Close()
+		if err != nil {
+			log.Error(err)
+		}
+	}
+	// return last error
+	return err
 }
 
 func (s *hbaseStore) UUID() string {
@@ -92,7 +108,8 @@ func (s *hbaseStore) UUID() string {
 }
 
 func (s *hbaseStore) CurrentVersion() (kv.Version, error) {
-	t := themis.NewTxn(s.cli)
+	hbaseCli := s.conns[time.Now().UnixNano()%hbaseConnPoolSize]
+	t := themis.NewTxn(hbaseCli)
 	defer t.Release()
 
 	return kv.Version{Ver: t.GetStartTS()}, nil
@@ -122,10 +139,18 @@ func (d Driver) Open(zkInfo string) (kv.Storage, error) {
 		return store, nil
 	}
 
-	c, err := hbase.NewClient(zks, "/hbase")
-	if err != nil {
-		return nil, errors.Trace(err)
+	// create buffered HBase connections, HBaseClient is goroutine-safe, so
+	// it's OK to redistribute to transactions.
+	conns := make([]hbase.HBaseClient, 0, hbaseConnPoolSize)
+	for i := 0; i < hbaseConnPoolSize; i++ {
+		c, err := hbase.NewClient(zks, "/hbase")
+		if err != nil {
+			return nil, errors.Trace(err)
+		}
+		conns = append(conns, c)
 	}
+
+	c := conns[0]
 	if !c.TableExists(tableName) {
 		// Create new hbase table for store.
 		t := hbase.NewTableDesciptor(hbase.NewTableNameWithDefaultNS(tableName))
@@ -137,10 +162,11 @@ func (d Driver) Open(zkInfo string) (kv.Storage, error) {
 			return nil, errors.Trace(err)
 		}
 	}
+
 	s := &hbaseStore{
 		zkInfo:    zkInfo,
 		storeName: tableName,
-		cli:       c,
+		conns:     conns,
 	}
 	mc.cache[zkInfo] = s
 	return s, nil