mirror of
https://github.com/seaweedfs/seaweedfs.git
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138 lines
3.8 KiB
Go
138 lines
3.8 KiB
Go
package storage
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import (
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"fmt"
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"os"
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"github.com/chrislusf/seaweedfs/weed/glog"
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"github.com/chrislusf/seaweedfs/weed/pb/master_pb"
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"github.com/chrislusf/seaweedfs/weed/storage/backend"
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"github.com/chrislusf/seaweedfs/weed/storage/needle"
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"github.com/chrislusf/seaweedfs/weed/util"
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"github.com/golang/protobuf/proto"
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)
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const (
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_SuperBlockSize = 8
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)
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/*
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* Super block currently has 8 bytes allocated for each volume.
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* Byte 0: version, 1 or 2
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* Byte 1: Replica Placement strategy, 000, 001, 002, 010, etc
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* Byte 2 and byte 3: Time to live. See TTL for definition
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* Byte 4 and byte 5: The number of times the volume has been compacted.
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* Rest bytes: Reserved
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*/
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type SuperBlock struct {
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version needle.Version
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ReplicaPlacement *ReplicaPlacement
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Ttl *needle.TTL
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CompactionRevision uint16
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Extra *master_pb.SuperBlockExtra
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extraSize uint16
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}
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func (s *SuperBlock) BlockSize() int {
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switch s.version {
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case needle.Version2, needle.Version3:
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return _SuperBlockSize + int(s.extraSize)
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}
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return _SuperBlockSize
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}
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func (s *SuperBlock) Version() needle.Version {
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return s.version
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}
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func (s *SuperBlock) Bytes() []byte {
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header := make([]byte, _SuperBlockSize)
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header[0] = byte(s.version)
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header[1] = s.ReplicaPlacement.Byte()
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s.Ttl.ToBytes(header[2:4])
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util.Uint16toBytes(header[4:6], s.CompactionRevision)
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if s.Extra != nil {
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extraData, err := proto.Marshal(s.Extra)
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if err != nil {
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glog.Fatalf("cannot marshal super block extra %+v: %v", s.Extra, err)
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}
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extraSize := len(extraData)
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if extraSize > 256*256-2 {
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// reserve a couple of bits for future extension
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glog.Fatalf("super block extra size is %d bigger than %d", extraSize, 256*256-2)
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}
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s.extraSize = uint16(extraSize)
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util.Uint16toBytes(header[6:8], s.extraSize)
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header = append(header, extraData...)
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}
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return header
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}
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func (s *SuperBlock) Initialized() bool {
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return s.ReplicaPlacement != nil && s.Ttl != nil
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}
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func (v *Volume) maybeWriteSuperBlock() error {
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datSize, _, e := v.DataBackend.GetStat()
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if e != nil {
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glog.V(0).Infof("failed to stat datafile %s: %v", v.DataBackend.Name(), e)
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return e
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}
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if datSize == 0 {
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v.SuperBlock.version = needle.CurrentVersion
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_, e = v.DataBackend.WriteAt(v.SuperBlock.Bytes(), 0)
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if e != nil && os.IsPermission(e) {
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//read-only, but zero length - recreate it!
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var dataFile *os.File
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if dataFile, e = os.Create(v.DataBackend.Name()); e == nil {
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v.DataBackend = backend.NewDiskFile(dataFile)
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if _, e = v.DataBackend.WriteAt(v.SuperBlock.Bytes(), 0); e == nil {
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v.noWriteOrDelete = false
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v.noWriteCanDelete = false
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}
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}
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}
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}
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return e
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}
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func (v *Volume) readSuperBlock() (err error) {
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v.SuperBlock, err = ReadSuperBlock(v.DataBackend)
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return err
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}
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// ReadSuperBlock reads from data file and load it into volume's super block
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func ReadSuperBlock(datBackend backend.BackendStorageFile) (superBlock SuperBlock, err error) {
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header := make([]byte, _SuperBlockSize)
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if _, e := datBackend.ReadAt(header, 0); e != nil {
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err = fmt.Errorf("cannot read volume %s super block: %v", datBackend.Name(), e)
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return
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}
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superBlock.version = needle.Version(header[0])
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if superBlock.ReplicaPlacement, err = NewReplicaPlacementFromByte(header[1]); err != nil {
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err = fmt.Errorf("cannot read replica type: %s", err.Error())
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return
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}
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superBlock.Ttl = needle.LoadTTLFromBytes(header[2:4])
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superBlock.CompactionRevision = util.BytesToUint16(header[4:6])
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superBlock.extraSize = util.BytesToUint16(header[6:8])
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if superBlock.extraSize > 0 {
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// read more
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extraData := make([]byte, int(superBlock.extraSize))
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superBlock.Extra = &master_pb.SuperBlockExtra{}
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err = proto.Unmarshal(extraData, superBlock.Extra)
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if err != nil {
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err = fmt.Errorf("cannot read volume %s super block extra: %v", datBackend.Name(), err)
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return
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}
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}
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return
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}
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