Package io.camunda.zeebe.journal

Interface JournalReader

All Superinterfaces:
AutoCloseable, Iterator<JournalRecord>
public interface JournalReader extends Iterator<JournalRecord>, AutoCloseable

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    close()
     
    long
    seek(long index)
    Seek to a record at the given index.
    long
    seekToAsqn(long asqn)
    Seek to a record with the highest ASQN less than or equal to the given asqn.
    long
    seekToAsqn(long asqn, long indexUpperBound)
    Seek to a record with the highest ASQN less than or equal to the given asqn, with the restriction that it seeks to a record with index less than or equal to the given indexUpperBound.
    long
    seekToFirst()
    Seek to the first index of the journal.
    long
    seekToLast()
    Seek to the last index of the journal.

    Methods inherited from interface java.util.Iterator

    forEachRemaining, hasNext, next, remove

  • Method Details

    • seek

      long seek(long index)
      Seek to a record at the given index. if seek(index) return true, Iterator.next() should return a record at index.

      If the journal is empty, it will return Journal.getFirstIndex(), but it should not do anything.

      If the index is less than Journal.getFirstIndex(), Iterator.next() should return a record at index Journal.getFirstIndex().

      If the index is greater than Journal.getLastIndex(), the read is positioned past the end of the journal, such that Iterator.hasNext() will return false. In this case, the returned index would be {@link Journal#getLastIndex()} + 1.

      Callers are expected to call Iterator.hasNext() after a seek, regardless of the result returned.

      Parameters:
      index - the index to seek to.
      Returns:
      the index of the next record to be read

    • seekToFirst

      long seekToFirst()
      Seek to the first index of the journal. The index returned is that of the record which would be returned by calling Iterator.next().

      Equivalent to calling seek(journal.getFirstIndex()).

      Callers are expected to call Iterator.hasNext() after a seek, regardless of the result returned.

      If the journal is empty, then the index returned is the Journal.getFirstIndex().

      Returns:
      the first index of the journal

    • seekToLast

      long seekToLast()
      Seek to the last index of the journal. The index returned is that of the record which would be returned by calling Iterator.next().

      Equivalent to calling seek(journal.getLastIndex()).

      Callers are expected to call Iterator.hasNext() after a seek, regardless of the result returned.

      If the journal is empty, then the index returned is the Journal.getLastIndex(), which may be lower than Journal.getFirstIndex().

      Returns:
      the last index of the journal

    • seekToAsqn

      long seekToAsqn(long asqn)
      Seek to a record with the highest ASQN less than or equal to the given asqn.

      If there are no records with a lower or equal ASQN, then the reader will be positioned at the beginning of the record. That is it behaves as if seekToFirst(). In this case it's possible that the next record has an ASQN of -1, as not all records have an ASQN assigned.

      Callers are expected to call Iterator.hasNext() after a seek, regardless of the result returned.

      The index returned is that of a valid record, or if the journal is empty, Journal.getFirstIndex().

      Parameters:
      asqn - application sequence number to seek
      Returns:
      the index of the record that will be returned by Iterator.next()

    • seekToAsqn

      long seekToAsqn(long asqn, long indexUpperBound)
      Seek to a record with the highest ASQN less than or equal to the given asqn, with the restriction that it seeks to a record with index less than or equal to the given indexUpperBound.

      Otherwise, the semantics is similar to seekToAsqn(asqn)

      Parameters:
      asqn - application sequence number to seek
      indexUpperBound - the index until which it seeks
      Returns:
      the index of the record that will be returned by Iterator.next()

    • close

      void close()
      Specified by:
      close in interface AutoCloseable