{"record":{"id":"263c32a66f7be542","repo":"juicedata/juicefs","slug":"failed-to-read-segment-type-v","errorCode":null,"errorMessage":"failed to read segment type: %v","messagePattern":"failed to read segment type: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/meta/backup.go","lineNumber":351,"sourceCode":"\tdata, err := proto.Marshal(s.val)\n\tif err != nil {\n\t\treturn 0, fmt.Errorf(\"failed to marshal segment message %s : %w\", s, err)\n\t}\n\ts.len = uint64(len(data))\n\tif err := binary.Write(w, binary.BigEndian, s.len); err != nil {\n\t\treturn 0, fmt.Errorf(\"failed to write segment length %s: %w\", s, err)\n\t}\n\n\tif n, err := w.Write(data); err != nil || n != len(data) {\n\t\treturn 0, fmt.Errorf(\"failed to write segment data %s: err %w, write len %d, expect len %d\", s, err, n, len(data))\n\t}\n\n\treturn binary.Size(s.typ) + binary.Size(s.len) + len(data), nil\n}\n\nfunc (s *BakSegment) Unmarshal(r io.Reader) error {\n\tif err := binary.Read(r, binary.BigEndian, &s.typ); err != nil {\n\t\treturn fmt.Errorf(\"failed to read segment type: %v\", err)\n\t}\n\n\tif s.typ == BakEOS {\n\t\treturn errBakEOF\n\t}\n\n\tif err := binary.Read(r, binary.BigEndian, &s.len); err != nil {\n\t\treturn fmt.Errorf(\"failed to read segment %s length: %v\", s, err)\n\t}\n\tdata := make([]byte, s.len)\n\tn, err := r.Read(data)\n\tif err != nil && n != int(s.len) {\n\t\treturn fmt.Errorf(\"failed to read segment value: err %v, read len %d, expect len %d\", err, n, s.len)\n\t}\n\n\tmsg, err := getMessageFromType(int(s.typ))\n\tif err != nil {\n\t\treturn fmt.Errorf(\"failed to create message by type %d: %w\", s.typ, err)","sourceCodeStart":333,"sourceCodeEnd":369,"githubUrl":"https://github.com/juicedata/juicefs/blob/c9a67b23e8e08ec23ec331aa6f1675e2319e921c/pkg/meta/backup.go#L333-L369","documentation":"BakSegment.Unmarshal reads the 1-byte segment type from the backup stream with binary.Read. This error is thrown when that read fails — almost always io.EOF or io.ErrUnexpectedEOF, meaning the stream ended before a segment type byte could be read. The caller (ReadFooter) treats errBakEOF (returned when typ == BakEOS) as a normal end marker; this error instead means the stream is truncated or unreadable without a valid EOS.","triggerScenarios":"Calling ReadFooter on a backup file/stream that is empty, truncated (partial write during backup), or whose read fails with an I/O error (bad file descriptor, read permission, corrupted medium).","commonSituations":"Loading a metadata backup file that was cut short by a failed/partial backup write; a corrupted or zero-byte backup file; reading from a closed or unreadable file handle.","solutions":["Verify the backup file is complete and non-empty (compare size against the original backup output or re-run the backup)","Check read permissions on the backup file and that the handle is open/valid","If the file is truncated, regenerate the backup rather than trying to salvage the footer","If EOF at a clean boundary is expected, handle errBakEOF, not this error"],"exampleFix":null,"handlingStrategy":"validation","validationCode":"fi, err := os.Stat(backupPath)\nif err != nil || fi.Size() == 0 { return fmt.Errorf(\"backup file missing or empty: %s\", backupPath) }","typeGuard":null,"tryCatchPattern":"if err := seg.Unmarshal(r); err != nil {\n    switch {\n    case errors.Is(err, errBakEOF): // clean end\n    case errors.Is(err, io.ErrUnexpectedEOF), errors.Is(err, io.EOF):\n        return fmt.Errorf(\"backup file truncated: %w\", err)\n    default:\n        return err\n    }\n}","preventionTips":["Verify backup file completeness (size/checksum) before loading","Ensure the backup process completed successfully before consuming its output","Avoid manually truncating or editing backup files"],"tags":["io","read-failed","eof","truncated-data","backup"],"backgroundTag":"file-read-failed","analyzedSha":"c9a67b23e8e08ec23ec331aa6f1675e2319e921c","analyzedAt":"2026-09-06T17:55:48.476Z","contentChangedAt":"2026-09-06T17:55:48.476Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}