david
9a322274a5
Append-only WAL with CRC32-validated records, automatic segment rotation at 128 MiB, background periodic fsync, and crash recovery by truncation at the first corrupt or incomplete record. Record format: type(1) | len(4) | payload | crc32c(4). Two payload types: series (ref + labels) and samples (batch of ref/t/v). Fixed-width encoding througout. Torn-write harness truncates at every byte offset and asserts recovery produces a valid prefix of the original sequnce, both single-segment and multi-segment. DESIGN.md, NOTICE.md, and README.md.
64 lines
1.4 KiB
Go
64 lines
1.4 KiB
Go
package wal
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import (
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"fmt"
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"os"
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"path/filepath"
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"sort"
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"strconv"
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)
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const (
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defaultSegmentMaxSize = 128 * 1024 * 1024 // 128 MiB
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segmentNameLen = 8 // "00000001"
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)
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// segmentFileName returns the zero-padded filename for a segment index.
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func segmentFileName(index int) string {
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return fmt.Sprintf("%0*d", segmentNameLen, index)
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}
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// parseSegmentIndex parses a segment filename back to its index.
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// Returns -1 if the name is not a valid segment file.
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func parseSegmentIndex(name string) int {
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if len(name) != segmentNameLen {
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return -1
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}
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n, err := strconv.Atoi(name)
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if err != nil {
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return -1
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}
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return n
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}
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// listSegments returns the sorted indices of all segment files in dir.
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func listSegments(dir string) ([]int, error) {
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entries, err := os.ReadDir(dir)
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if err != nil {
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return nil, err
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}
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var indices []int
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for _, e := range entries {
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if e.IsDir() {
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continue
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}
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idx := parseSegmentIndex(e.Name())
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if idx >= 0 {
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indices = append(indices, idx)
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}
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}
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sort.Ints(indices)
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return indices, nil
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}
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// segmentPath returns the full path for a segment index within dir.
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func segmentPath(dir string, index int) string {
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return filepath.Join(dir, segmentFileName(index))
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}
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// createSegment creates a new segment file and returns it open for writing.
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func createSegment(dir string, index int) (*os.File, error) {
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return os.OpenFile(segmentPath(dir, index), os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0644)
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}
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