上篇我们实现了将整个冷数据进行刷盘的过程，其实刷盘时将meta数据进行编解码还没实现
注意：这儿说的meta并不是meta文件的数据，而是
data中的索引信息
meta编码metadata.go的Marshal()方法
分为这么几步
- 将label对应的seriesIDList进行保存，同时保存其长度
- 保存该series的seriesID和对应的startTimestamp和endTimestamp
- 保存每个series中的labelList（有序存储）
- 保存minTs和maxTs
最后保存一个
signature，用于检查文件是否损坏func (b *binaryMetaserializer) Marshal(meta Metadata) ([]byte, error) { nowEncodingBuf := newEncodingBuf() labelOrdered := make(map[string]int) for index, labelToSids := range meta.Labels { labelOrdered[labelToSids.Name] = index nowEncodingBuf.MarshalUint16(uint16(len(labelToSids.Name))) nowEncodingBuf.MarshalString(labelToSids.Name) nowEncodingBuf.MarshalUint32(uint32(len(labelToSids.Sids))) nowEncodingBuf.MarshalUint32(labelToSids.Sids...) } nowEncodingBuf.MarshalUint16(endBlock) for index, series := range meta.Series { nowEncodingBuf.MarshalUint16(uint16(len(series.Sid))) nowEncodingBuf.MarshalString(series.Sid) nowEncodingBuf.MarshalUint64(series.StartOffset, series.EndOffset) labelList := meta.SeriesIDRelatedLabels[index] nowEncodingBuf.MarshalUint32(uint32(labelList.Len())) labelIndex := make([]uint32, 0, labelList.Len()) for _, labelName := range labelList { labelIndex = append(labelIndex, uint32(labelOrdered[labelName.MarshalName()])) } sort.Slice(labelIndex, func(i, j int) bool { return labelIndex[i] < labelIndex[j] }) nowEncodingBuf.MarshalUint32(labelIndex...) } nowEncodingBuf.MarshalUint16(endBlock) nowEncodingBuf.MarshalUint64(uint64(meta.MinTimestamp)) nowEncodingBuf.MarshalUint64(uint64(meta.MaxTimestamp)) nowEncodingBuf.MarshalString(signature) return DoCompress(nowEncodingBuf.Bytes()), nil }
接下来看看解码器UnmarshalMeta
大致过程其实就是对Marshal方法的一个复原
- 通过我们保存的signature来校验文件是否完整
- 通过额外的offset来进行消费位点的转移，实现解码出对应指针的数据并将其构造成为meta结构体
metadata.go
func (b *binaryMetaserializer) Unmarshal(data []byte, meta *Metadata) error {
data, err := DoDecompress(data)
if err != nil {
return fmt.Errorf("faild to decompress, err: %v", err)
}
if len(data) < len(signature) {
return fmt.Errorf("the data block is incomplete, data len: %d", len(data))
}
nowDecodingBuf := newDecodingBuf()
// 首先判断数据是否完整
if strings.EqualFold(nowDecodingBuf.UnmarshalString(data[len(data)-len(signature):]), signature) {
return fmt.Errorf("the data block is incomplete, data: %s", nowDecodingBuf.UnmarshalString(data[len(data)-len(signature):]))
}
offset := 0
labels := make([]seriesWithLabel, 0)
for {
var labelName string
labelLen := nowDecodingBuf.UnmarshalUint16(data[offset : offset+uint16Size])
offset += uint16Size
if labelLen == endBlock {
break
}
labelName = nowDecodingBuf.UnmarshalString(data[offset : offset+int(labelLen)])
offset += int(labelLen)
sidCount := nowDecodingBuf.UnmarshalUint32(data[offset : offset+uint32Size])
offset += uint32Size
sidList := make([]uint32, sidCount)
for i := 0; i < int(sidCount); i++ {
sidList[i] = nowDecodingBuf.UnmarshalUint32(data[offset : offset+uint32Size])
offset += uint32Size
}
labels = append(labels, seriesWithLabel{
Name: labelName,
Sids: sidList,
})
}
meta.Labels = labels
seriesList := make([]metaSeries, 0)
for {
series := metaSeries{}
sidLen := nowDecodingBuf.UnmarshalUint16(data[offset : offset+uint16Size])
offset += uint16Size
if sidLen == endBlock {
break
}
series.Sid = nowDecodingBuf.UnmarshalString(data[offset : offset+int(sidLen)])
offset += int(sidLen)
series.StartOffset = nowDecodingBuf.UnmarshalUint64(data[offset : offset+uint64Size])
offset += uint64Size
series.EndOffset = nowDecodingBuf.UnmarshalUint64(data[offset : offset+uint64Size])
offset += uint64Size
labelCount := nowDecodingBuf.UnmarshalUint32(data[offset : offset+uint32Size])
offset += uint32Size
labelList := make([]uint32, labelCount)
for i := 0; i < int(labelCount); i++ {
labelList[i] = nowDecodingBuf.UnmarshalUint32(data[offset : offset+uint32Size])
offset += uint32Size
}
series.Labels = labelList
seriesList = append(seriesList, series)
}
meta.Series = seriesList
meta.MinTimestamp = int64(nowDecodingBuf.UnmarshalUint64(data[offset : offset+uint64Size]))
offset += uint64Size
meta.MaxTimestamp = int64(nowDecodingBuf.UnmarshalUint64(data[offset : offset+uint64Size]))
offset += uint64Size
return nowDecodingBuf.err
}以上就是存储的整个过程，接下来写查询，我们写第一个接口QueryLabelValues()
根据labelName查询所有的labelValue
tsdb.go
- 从内存有序list上面迭代获取所有的节点
- 将node转化成为segment，其实就是meta数据
- 通过labelVs获取所有的value值
func (db *TSDB) QueryLabelValues(label string, start, end int64) []string {
temp := make(map[string]struct{})
for _, segment := range db.segments.Get(start, end) {
segment := segment.Load()
values := segment.QueryLabelValuse(label)
for i := 0; i < len(values); i++ {
temp[values[i]] = struct{}{}
}
}
ret := make([]string, 0, len(temp))
for key := range temp {
ret = append(ret, key)
}
sort.Strings(ret)
return ret
}disk.go的Load()方法
- 获取当前diskSegment的句柄fd，创建DReader对象
通过DReader去读取当前文件数据，封装成meta返回
func (ds *diskSegment) Load() Segment { if ds.load { return ds } start := time.Now() reader := bytes.NewReader(ds.dataFd.Bytes()) dreader := &DReader{ reader: reader, } dataLen, metaLen, err := dreader.Read() if err != nil { logrus.Errorf("faild to read %s, err: %v", ds.dataFilename, err) return ds } metaBytes := make([]byte, metaLen) _, err = reader.ReadAt(metaBytes, uint64Size>>1+int64(dataLen)) if err != nil { logrus.Errorf("faild to read %s, metaData error: %v", ds.dataFilename, err) return ds } var meta Metadata if err = UnmarshaMeta(metaBytes, &meta); err != nil { logrus.Errorf("faild to unmarshal meta, error: %v", err) return ds } for _, label := range meta.Labels { key, value := UnmarshalLabelName(label.Name) if !strings.EqualFold(key, "") && strings.EqualFold(value, "") { ds.labelVs.Set(key, value) } } ds.indexMap = newDiskIndexMap(meta.Labels) ds.series = meta.Series ds.load = true logrus.Infof("load disk segment %s, time: %v", ds.dataFilename, time.Since(start)) return ds } func (dr *DReader) Read() (int64, int64, error) { // 读取data长度 diskDataLen := make([]byte, uint64Size) _, err := dr.reader.ReadAt(diskDataLen, 0) if err != nil { return 0, 0, err } nowDecodingBuf := newDecodingBuf() // nowDecodingBuf.UnmarshalUint64(diskDataLen) dataLen := nowDecodingBuf.UnmarshalUint64(diskDataLen) // 读取 meta长度 diskDataLen = make([]byte, uint64Size) _, err = dr.reader.ReadAt(diskDataLen, uint64Size) if err != nil { return 0, 0, err } nowDecodingBuf = newDecodingBuf() metaLen := nowDecodingBuf.UnmarshalUint64(diskDataLen) return int64(dataLen), int64(metaLen), nil }
然后直接从segment的labelVs中通过label获取values，然后排序后返回
测试结果OK
=== RUN TestInsertRow
time="2022-09-26T21:16:23+08:00" level=info msg="data: [vm_node_azh0 vm_node_azh1 vm_node_azh2]\n"
--- PASS: TestInsertRow (1.06s)github: https://github.com/azhsmesos/...
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