Add boltdb for volume needle map

boltdb is fairly slow to write, about 6 minutes for recreating index
for 1553934 files. Boltdb loads 1,553,934 x 16 = 24,862,944bytes from
disk, and generate the boltdb as large as 134,217,728 bytes in 6
minutes.

To compare, for leveldb, it recreates index in leveldb as large as
27,188,148 bytes in 8 seconds.
For in memory version, it loads the index in

To test the memory consumption, the leveldb or boltdb index are
created. And the server is restarted. Using the benchmark tool to read
lots of files. There are 7 volumes in benchmark collection, each with
about 1553K files.
For leveldb, the memory starts at 142,884KB, and stays at 179,340KB.
For boltdb, the memory starts at 73,756KB, and stays at 144,564KB.
For in-memory, the memory starts at 368,152KB, and stays at 448,032KB.

1 files changed, 24 insertions, 14 deletions

diff --git a/go/storage/volume.go b/go/storage/volume.go
index 2b47fb497..e35eeee49 100644
--- a/go/storage/volume.go
+++ b/go/storage/volume.go
@@ -14,12 +14,13 @@ import (
 )
 
 type Volume struct {
-	Id         VolumeId
-	dir        string
-	Collection string
-	dataFile   *os.File
-	nm         NeedleMapper
-	readOnly   bool
+	Id            VolumeId
+	dir           string
+	Collection    string
+	dataFile      *os.File
+	nm            NeedleMapper
+	needleMapKind NeedleMapType
+	readOnly      bool
 
 	SuperBlock
 
@@ -27,20 +28,22 @@ type Volume struct {
 	lastModifiedTime uint64 //unix time in seconds
 }
 
-func NewVolume(dirname string, collection string, id VolumeId, useLevelDb bool, replicaPlacement *ReplicaPlacement, ttl *TTL) (v *Volume, e error) {
+func NewVolume(dirname string, collection string, id VolumeId, needleMapKind NeedleMapType, replicaPlacement *ReplicaPlacement, ttl *TTL) (v *Volume, e error) {
 	v = &Volume{dir: dirname, Collection: collection, Id: id}
 	v.SuperBlock = SuperBlock{ReplicaPlacement: replicaPlacement, Ttl: ttl}
-	e = v.load(true, true, useLevelDb)
+	v.needleMapKind = needleMapKind
+	e = v.load(true, true, needleMapKind)
 	return
 }
 func (v *Volume) String() string {
 	return fmt.Sprintf("Id:%v, dir:%s, Collection:%s, dataFile:%v, nm:%v, readOnly:%v", v.Id, v.dir, v.Collection, v.dataFile, v.nm, v.readOnly)
 }
 
-func loadVolumeWithoutIndex(dirname string, collection string, id VolumeId) (v *Volume, e error) {
+func loadVolumeWithoutIndex(dirname string, collection string, id VolumeId, needleMapKind NeedleMapType) (v *Volume, e error) {
 	v = &Volume{dir: dirname, Collection: collection, Id: id}
 	v.SuperBlock = SuperBlock{}
-	e = v.load(false, false, false)
+	v.needleMapKind = needleMapKind
+	e = v.load(false, false, needleMapKind)
 	return
 }
 func (v *Volume) FileName() (fileName string) {
@@ -51,7 +54,7 @@ func (v *Volume) FileName() (fileName string) {
 	}
 	return
 }
-func (v *Volume) load(alsoLoadIndex bool, createDatIfMissing bool, useLevelDb bool) error {
+func (v *Volume) load(alsoLoadIndex bool, createDatIfMissing bool, needleMapKind NeedleMapType) error {
 	var e error
 	fileName := v.FileName()
 
@@ -99,16 +102,22 @@ func (v *Volume) load(alsoLoadIndex bool, createDatIfMissing bool, useLevelDb bo
 				return fmt.Errorf("cannot write Volume Index %s.idx: %v", fileName, e)
 			}
 		}
-		if !useLevelDb {
+		switch needleMapKind {
+		case NeedleMapInMemory:
 			glog.V(0).Infoln("loading index file", fileName+".idx", "readonly", v.readOnly)
 			if v.nm, e = LoadNeedleMap(indexFile); e != nil {
 				glog.V(0).Infof("loading index %s error: %v", fileName+".idx", e)
 			}
-		} else {
+		case NeedleMapLevelDb:
 			glog.V(0).Infoln("loading leveldb file", fileName+".ldb")
 			if v.nm, e = NewLevelDbNeedleMap(fileName+".ldb", indexFile); e != nil {
 				glog.V(0).Infof("loading leveldb %s error: %v", fileName+".ldb", e)
 			}
+		case NeedleMapBoltDb:
+			glog.V(0).Infoln("loading boltdb file", fileName+".bdb")
+			if v.nm, e = NewBoltDbNeedleMap(fileName+".bdb", indexFile); e != nil {
+				glog.V(0).Infof("loading boltdb %s error: %v", fileName+".bdb", e)
+			}
 		}
 	}
 	return e
@@ -263,11 +272,12 @@ func (v *Volume) read(n *Needle) (int, error) {
 }
 
 func ScanVolumeFile(dirname string, collection string, id VolumeId,
+	needleMapKind NeedleMapType,
 	visitSuperBlock func(SuperBlock) error,
 	readNeedleBody bool,
 	visitNeedle func(n *Needle, offset int64) error) (err error) {
 	var v *Volume
-	if v, err = loadVolumeWithoutIndex(dirname, collection, id); err != nil {
+	if v, err = loadVolumeWithoutIndex(dirname, collection, id, needleMapKind); err != nil {
 		return fmt.Errorf("Failed to load volume %d: %v", id, err)
 	}
 	if err = visitSuperBlock(v.SuperBlock); err != nil {