Package org.apache.hadoop.hdfs.server.protocol

Interface JournalProtocol

All Known Implementing Classes:
JournalProtocolTranslatorPB
@Private public interface JournalProtocol
Protocol used to journal edits to a remote node. Currently, this is used to publish edits from the NameNode to a BackupNode.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final long
    versionID
    This class is used by both the Namenode (client) and BackupNode (server) to insulate from the protocol serialization.

  • Method Summary

    Modifier and Type
    Method
    Description
    FenceResponse
    fence(JournalInfo journalInfo, long epoch, String fencerInfo)
    Request to fence any other journal writers.
    void
    journal(JournalInfo journalInfo, long epoch, long firstTxnId, int numTxns, byte[] records)
    Journal edit records.
    void
    startLogSegment(JournalInfo journalInfo, long epoch, long txid)
    Notify the BackupNode that the NameNode has rolled its edit logs and is now writing a new log segment.

  • Field Details

    • versionID

      static final long versionID
      This class is used by both the Namenode (client) and BackupNode (server) to insulate from the protocol serialization. If you are adding/changing DN's interface then you need to change both this class and ALSO related protocol buffer wire protocol definition in JournalProtocol.proto. For more details on protocol buffer wire protocol, please see .../org/apache/hadoop/hdfs/protocolPB/overview.html
      See Also:

  • Method Details

    • journal

      void journal(JournalInfo journalInfo, long epoch, long firstTxnId, int numTxns, byte[] records) throws IOException
      Journal edit records. This message is sent by the active name-node to the backup node via EditLogBackupOutputStream in order to synchronize meta-data changes with the backup namespace image.
      Parameters:
      journalInfo - journal information
      epoch - marks beginning a new journal writer
      firstTxnId - the first transaction of this batch
      numTxns - number of transactions
      records - byte array containing serialized journal records
      Throws:
      FencedException - if the resource has been fenced
      IOException

    • startLogSegment

      void startLogSegment(JournalInfo journalInfo, long epoch, long txid) throws IOException
      Notify the BackupNode that the NameNode has rolled its edit logs and is now writing a new log segment.
      Parameters:
      journalInfo - journal information
      epoch - marks beginning a new journal writer
      txid - the first txid in the new log
      Throws:
      FencedException - if the resource has been fenced
      IOException

    • fence

      FenceResponse fence(JournalInfo journalInfo, long epoch, String fencerInfo) throws IOException
      Request to fence any other journal writers. Older writers with at previous epoch will be fenced and can no longer perform journal operations.
      Parameters:
      journalInfo - journal information
      epoch - marks beginning a new journal writer
      fencerInfo - info about fencer for debugging purposes
      Throws:
      FencedException - if the resource has been fenced
      IOException