Tamás Gulácsi contributed cdb map for read only extremely low memory

implementation.
This commit is contained in:
Chris Lu 2013-05-05 11:19:41 -07:00
parent fb635146a1
commit 715d327df0
2 changed files with 398 additions and 0 deletions

230
go/storage/cdb_map.go Normal file
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package storage
import (
"code.google.com/p/weed-fs/go/util"
"encoding/json"
"errors"
"fmt"
"github.com/tgulacsi/go-cdb"
"os"
"path/filepath"
)
// CDB-backed read-only needle map
type cdbMap struct {
c1, c2 *cdb.Cdb
fn1, fn2 string
mapMetric
}
const maxCdbRecCount = 100000000
var errReadOnly = errors.New("cannot modify a read-only map")
// opens the cdb file(s) (base.cdb OR base.1.cdb AND base.2.cdb)
// in case of two files, the metric (at key 'M') must be in base.2.cdb
func OpenCdbMap(fileName string) (m *cdbMap, err error) {
m = new(cdbMap)
if m.c1, err = cdb.Open(fileName); err == nil {
m.fn1 = fileName
err = getMetric(m.c1, &m.mapMetric)
return
}
if os.IsNotExist(err) {
bn, ext := nakeFilename(fileName)
m.fn1 = bn + ".1" + ext
if m.c1, err = cdb.Open(m.fn1); err != nil {
return nil, err
}
m.fn2 = bn + ".2" + ext
if m.c2, err = cdb.Open(m.fn2); err != nil {
return nil, err
}
err = getMetric(m.c2, &m.mapMetric)
return
}
return nil, err
}
func (m *cdbMap) Put(key uint64, offset uint32, size uint32) (int, error) {
return -1, errReadOnly
}
func (m *cdbMap) Delete(key uint64) error {
return errReadOnly
}
func (m *cdbMap) Close() {
if m.c2 != nil {
m.c2.Close()
m.c2 = nil
}
if m.c1 != nil {
m.c1.Close()
m.c1 = nil
}
}
func (m cdbMap) ContentSize() uint64 {
return m.FileByteCounter
}
func (m cdbMap) DeletedSize() uint64 {
return m.DeletionByteCounter
}
func (m cdbMap) FileCount() int {
return m.FileCounter
}
func (m *cdbMap) DeletedCount() int {
return m.DeletionCounter
}
func getMetric(c *cdb.Cdb, m *mapMetric) error {
data, err := c.Data([]byte{'M'})
if err != nil {
return err
}
return json.Unmarshal(data, m)
}
func (m cdbMap) Get(key uint64) (element *NeedleValue, ok bool) {
var (
data []byte
k []byte = make([]byte, 8)
err error
)
util.Uint64toBytes(k, key)
if data, err = m.c1.Data(k); err != nil || data == nil {
if m.c2 == nil {
return nil, false
}
if data, err = m.c2.Data(k); err != nil || data == nil {
return nil, false
}
}
return &NeedleValue{Key: Key(key), Offset: util.BytesToUint32(data[:4]),
Size: util.BytesToUint32(data[4:])}, true
}
func (m cdbMap) Visit(visit func(NeedleValue) error) (err error) {
fh, err := os.Open(m.fn1)
if err != nil {
return fmt.Errorf("cannot open %s: %s", m.fn1, err)
}
defer fh.Close()
walk := func(elt cdb.Element) error {
if len(elt.Key) != 8 {
return nil
}
return visit(NeedleValue{Key: Key(util.BytesToUint64(elt.Key)),
Offset: util.BytesToUint32(elt.Data[:4]),
Size: util.BytesToUint32(elt.Data[4:8])})
}
if err = cdb.DumpMap(fh, walk); err != nil {
return err
}
if m.c2 == nil {
return nil
}
fh.Close()
if fh, err = os.Open(m.fn2); err != nil {
return fmt.Errorf("cannot open %s: %s", m.fn2, err)
}
return cdb.DumpMap(fh, walk)
}
// converts an .idx index to a cdb
func ConvertIndexToCdb(cdbName string, index *os.File) error {
idx, err := LoadNeedleMap(index)
if err != nil {
return fmt.Errorf("error loading needle map %s: %s", index, err)
}
defer idx.Close()
return DumpNeedleMapToCdb(cdbName, idx)
}
// dumps a NeedleMap into a cdb
func DumpNeedleMapToCdb(cdbName string, nm *NeedleMap) error {
tempnam := cdbName + "t"
fnames := make([]string, 1, 2)
adder, closer, err := openTempCdb(tempnam)
if err != nil {
return fmt.Errorf("error creating factory: %s", err)
}
fnames[0] = tempnam
elt := cdb.Element{Key: make([]byte, 8), Data: make([]byte, 8)}
fcount := uint64(0)
walk := func(key uint64, offset, size uint32) error {
if fcount >= maxCdbRecCount {
if err = closer(); err != nil {
return err
}
tempnam = cdbName + "t2"
if adder, closer, err = openTempCdb(tempnam); err != nil {
return fmt.Errorf("error creating second factory: %s", err)
}
fnames = append(fnames, tempnam)
fcount = 0
}
util.Uint64toBytes(elt.Key, key)
util.Uint32toBytes(elt.Data[:4], offset)
util.Uint32toBytes(elt.Data[4:], size)
fcount++
return adder(elt)
}
// and write out the cdb from there
err = nm.Visit(func(nv NeedleValue) error {
return walk(uint64(nv.Key), nv.Offset, nv.Size)
})
if err != nil {
closer()
return fmt.Errorf("error walking index %s: %s", nm, err)
}
// store fileBytes
data, e := json.Marshal(nm.mapMetric)
if e != nil {
return fmt.Errorf("error marshaling metric %s: %s", nm.mapMetric, e)
}
if err = adder(cdb.Element{Key: []byte{'M'}, Data: data}); err != nil {
return err
}
if err = closer(); err != nil {
return err
}
os.Remove(cdbName)
if len(fnames) == 1 {
return os.Rename(fnames[0], cdbName)
}
bn, ext := nakeFilename(cdbName)
if err = os.Rename(fnames[0], bn+".1"+ext); err != nil {
return err
}
return os.Rename(fnames[1], bn+".2"+ext)
}
func openTempCdb(fileName string) (cdb.AdderFunc, cdb.CloserFunc, error) {
fh, err := os.Create(fileName)
if err != nil {
return nil, nil, fmt.Errorf("cannot create cdb file %s: %s", fileName, err)
}
adder, closer, err := cdb.MakeFactory(fh)
if err != nil {
fh.Close()
return nil, nil, fmt.Errorf("error creating factory: %s", err)
}
return adder, func() error {
if e := closer(); e != nil {
fh.Close()
return e
}
fh.Close()
return nil
}, nil
}
// returns filename without extension, and the extension
func nakeFilename(fileName string) (string, string) {
ext := filepath.Ext(fileName)
return fileName[:len(fileName)-len(ext)], ext
}

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go/storage/cdb_map_test.go Normal file
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package storage
import (
"log"
"math/rand"
"os"
"runtime"
"testing"
)
var testIndexFilename string = "../../test/sample.idx"
func TestCdbMap0Convert(t *testing.T) {
indexFile, err := os.Open(testIndexFilename)
if err != nil {
t.Fatalf("cannot open %s: %s", testIndexFilename, err)
}
defer indexFile.Close()
cdbFn := testIndexFilename + ".cdb"
t.Logf("converting %s to %s", cdbFn, cdbFn)
if err = ConvertIndexToCdb(cdbFn, indexFile); err != nil {
t.Fatalf("error while converting: %s", err)
}
}
func TestCdbMap1Mem(t *testing.T) {
var nm NeedleMapper
i := 0
visit := func(nv NeedleValue) error {
i++
return nil
}
a := getMemStats()
t.Logf("opening %s.cdb", testIndexFilename)
nm, err := OpenCdbMap(testIndexFilename + ".cdb")
if err != nil {
t.Fatalf("error opening cdb: %s", err)
}
b := getMemStats()
log.Printf("opening cdb consumed %d bytes", b-a)
defer nm.Close()
a = getMemStats()
if err = nm.Visit(visit); err != nil {
t.Fatalf("error visiting %s: %s", nm, err)
}
b = getMemStats()
log.Printf("visit cdb %d consumed %d bytes", i, b-a)
nm.Close()
indexFile, err := os.Open(testIndexFilename)
if err != nil {
t.Fatalf("error opening idx: %s", err)
}
a = getMemStats()
nm, err = LoadNeedleMap(indexFile)
if err != nil {
t.Fatalf("error loading idx: %s", err)
}
defer nm.Close()
b = getMemStats()
log.Printf("opening idx consumed %d bytes", b-a)
i = 0
a = getMemStats()
if err = nm.Visit(visit); err != nil {
t.Fatalf("error visiting %s: %s", nm, err)
}
b = getMemStats()
log.Printf("visit idx %d consumed %d bytes", i, b-a)
}
func BenchmarkCdbMap9List(t *testing.B) {
t.StopTimer()
indexFile, err := os.Open(testIndexFilename)
if err != nil {
t.Fatalf("cannot open %s: %s", testIndexFilename, err)
}
defer indexFile.Close()
a := getMemStats()
t.Logf("opening %s", indexFile)
idx, err := LoadNeedleMap(indexFile)
if err != nil {
t.Fatalf("cannot load %s: %s", indexFile, err)
}
defer idx.Close()
b := getMemStats()
log.Printf("LoadNeedleMap consumed %d bytes", b-a)
cdbFn := testIndexFilename + ".cdb"
a = getMemStats()
t.Logf("opening %s", cdbFn)
m, err := OpenCdbMap(cdbFn)
if err != nil {
t.Fatalf("error opening %s: %s", cdbFn, err)
}
defer m.Close()
b = getMemStats()
log.Printf("OpenCdbMap consumed %d bytes", b-a)
i := 0
log.Printf("checking whether the cdb contains every key")
t.StartTimer()
err = idx.Visit(func(nv NeedleValue) error {
if i > t.N || rand.Intn(10) < 9 {
return nil
}
i++
if i%1000 == 0 {
log.Printf("%d. %s", i, nv)
}
if nv2, ok := m.Get(uint64(nv.Key)); !ok || nv2 == nil {
t.Errorf("%s in index, not in cdb", nv.Key)
} else if nv2.Key != nv.Key {
t.Errorf("requested key %d from cdb, got %d", nv.Key, nv2.Key)
} else if nv2.Offset != nv.Offset {
t.Errorf("offset is %d in index, %d in cdb", nv.Offset, nv2.Offset)
} else if nv2.Size != nv.Size {
t.Errorf("size is %d in index, %d in cdb", nv.Size, nv2.Size)
}
t.SetBytes(int64(nv.Size))
return nil
})
t.StopTimer()
if err != nil {
t.Errorf("error visiting index: %s", err)
}
i = 0
log.Printf("checking wheter the cdb contains no stray keys")
t.StartTimer()
err = m.Visit(func(nv NeedleValue) error {
if i > t.N || rand.Intn(10) < 9 {
return nil
}
if nv2, ok := m.Get(uint64(nv.Key)); !ok || nv2 == nil {
t.Errorf("%s in cdb, not in index", nv.Key)
} else if nv2.Key != nv.Key {
t.Errorf("requested key %d from index, got %d", nv.Key, nv2.Key)
} else if nv2.Offset != nv.Offset {
t.Errorf("offset is %d in cdb, %d in index", nv.Offset, nv2.Offset)
} else if nv2.Size != nv.Size {
t.Errorf("size is %d in cdb, %d in index", nv.Size, nv2.Size)
}
i++
if i%1000 == 0 {
log.Printf("%d. %s", i, nv)
}
t.SetBytes(int64(nv.Size))
return nil
})
t.StopTimer()
if err != nil {
t.Errorf("error visiting index: %s", err)
}
}
var mem = new(runtime.MemStats)
// returns MemStats.Alloc after a GC
func getMemStats() int64 {
runtime.GC()
runtime.ReadMemStats(mem)
return int64(mem.Alloc)
}