/// <summary>
/// Notify the BackupNode that the NameNode has rolled its edit logs
/// and is now writing a new log segment.
/// </summary>
/// <param name="journalInfo">journal information</param>
/// <param name="epoch">marks beginning a new journal writer</param>
/// <param name="txid">the first txid in the new log</param>
/// <exception cref="FencedException">if the resource has been fenced</exception>
/// <exception cref="System.IO.IOException"/>
public abstract void StartLogSegment(JournalInfo journalInfo, long epoch, long txid
);
/// <summary>Request to fence any other journal writers.</summary>
/// <remarks>
/// Request to fence any other journal writers.
/// Older writers with at previous epoch will be fenced and can no longer
/// perform journal operations.
/// </remarks>
/// <param name="journalInfo">journal information</param>
/// <param name="epoch">marks beginning a new journal writer</param>
/// <param name="fencerInfo">info about fencer for debugging purposes</param>
/// <exception cref="FencedException">if the resource has been fenced</exception>
/// <exception cref="System.IO.IOException"/>
public abstract FenceResponse Fence(JournalInfo journalInfo, long epoch, string fencerInfo
);
/// <summary>Journal edit records.</summary>
/// <remarks>
/// Journal edit records.
/// This message is sent by the active name-node to the backup node
/// via
/// <c>EditLogBackupOutputStream</c>
/// in order to synchronize meta-data
/// changes with the backup namespace image.
/// </remarks>
/// <param name="journalInfo">journal information</param>
/// <param name="epoch">marks beginning a new journal writer</param>
/// <param name="firstTxnId">the first transaction of this batch</param>
/// <param name="numTxns">number of transactions</param>
/// <param name="records">byte array containing serialized journal records</param>
/// <exception cref="FencedException">if the resource has been fenced</exception>
/// <exception cref="System.IO.IOException"/>
public abstract void Journal(JournalInfo journalInfo, long epoch, long firstTxnId
, int numTxns, byte[] records);
