Function recover

nodedb-wal/src/recovery.rs:49–89

Scan a WAL file and recover the committed prefix. Returns `RecoveryInfo` describing the state of the WAL, or an error if the file cannot be opened.

(path: &Path)

/// Returns `RecoveryInfo` describing the state of the WAL, or an error
/// if the file cannot be opened.
pub fn recover(path: &Path) -> Result<RecoveryInfo> {
    if !path.exists() {
        return Ok(RecoveryInfo {
            last_lsn: 0,
            record_count: 0,
            end_offset: 0,
        });
    }

    let mut reader = WalReader::open(path)?;
    let mut last_lsn = 0u64;
    let mut record_count = 0u64;
    let mut last_valid_offset = 0u64;

    loop {
        let offset_before = reader.offset();
        match reader.next_record() {
            Ok(Some(record)) => {
                last_lsn = record.header.lsn;
                record_count += 1;
                last_valid_offset =
                    offset_before + HEADER_SIZE as u64 + record.header.payload_len as u64;
            }
            Ok(None) => {
                // End of committed prefix (EOF or corruption).
                break;
            }
            Err(e @ WalError::UnknownRequiredRecordType { .. }) => {
                // Cannot proceed past unknown required records.
                return Err(e);
            }
            Err(e) => return Err(e),
        }
    }

    Ok(RecoveryInfo {
        last_lsn,
        record_count,
        end_offset: last_valid_offset,
    })
}

#[cfg(test)]
mod tests {