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5.3 KiB
5.3 KiB
Memory Snapshot Format
Memory snapshot uses the WAL package and writes each series as a WAL record. Below are the formats of the individual records.
Series records
This record is a snapshot of a single series. Only one series exists per record. It includes the metadata of the series and the in-memory chunk data if it exists. The sampleBuf is the last 4 samples in the in-memory chunk.
┌──────────────────────────┬────────────────────────────┐
│ Record Type <byte> │ Series Ref <uint64> │
├──────────────────────────┴────────────────────────────┤
│ Number of Labels <uvarint> │
├──────────────────────────────┬────────────────────────┤
│ len(name_1) <uvarint> │ name_1 <bytes> │
├──────────────────────────────┼────────────────────────┤
│ len(val_1) <uvarint> │ val_1 <bytes> │
├──────────────────────────────┴────────────────────────┤
│ . . . │
├──────────────────────────────┬────────────────────────┤
│ len(name_N) <uvarint> │ name_N <bytes> │
├──────────────────────────────┼────────────────────────┤
│ len(val_N) <uvarint> │ val_N <bytes> │
├──────────────────────────────┴────────────────────────┤
│ Chunk Range <int64> │
├───────────────────────────────────────────────────────┤
│ Chunk Exists <uvarint> │
│ # 1 if head chunk exists, 0 otherwise to detect a nil |
| # chunk. Below fields exists only when it's 1 here. |
├───────────────────────────┬───────────────────────────┤
│ Chunk Mint <int64> │ Chunk Maxt <int64> │
├───────────────────────────┴───────────────────────────┤
│ Chunk Encoding <byte> │
├──────────────────────────────┬────────────────────────┤
│ len(Chunk) <uvarint> │ Chunk <bytes> │
├──────────────────────────┬───┴────────────────────────┤
| sampleBuf[0].t <int64> | sampleBuf[0].v <float64> |
├──────────────────────────┼────────────────────────────┤
| sampleBuf[1].t <int64> | sampleBuf[1].v <float64> |
├──────────────────────────┼────────────────────────────┤
| sampleBuf[2].t <int64> | sampleBuf[2].v <float64> |
├──────────────────────────┼────────────────────────────┤
| sampleBuf[3].t <int64> | sampleBuf[3].v <float64> |
└──────────────────────────┴────────────────────────────┘
Tombstone record
This includes all the tombstones in the Head block. A single record is written into the snapshot for all the tombstones. The encoded tombstones uses the same encoding as tombstone file in blocks.
┌─────────────────────────────────────────────────────────────────┐
│ Record Type <byte> │
├───────────────────────────────────┬─────────────────────────────┤
│ len(Encoded Tombstones) <uvarint> │ Encoded Tombstones <bytes> │
└───────────────────────────────────┴─────────────────────────────┘