Package com.mckoi.store

Class JournalledSystem.JournalFile

  • Enclosing class:
    JournalledSystem
    private final class JournalledSystem.JournalFile
extends java.lang.Object
    A JournalFile represents a file in which modification are logged out to when changes are made. A JournalFile contains instructions for rebuilding a resource to a known stable state.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private byte[] buffer
      Small buffer.
      private long cur_seq_id
      The sequence id for resources modified in this log.
      private StreamFile data
      The StreamFile object for reading and writing entries to/from the journal.
      private java.io.DataOutputStream data_out
      A DataOutputStream object used to write entries to the journal file.
      private java.io.File file
      The File object of this journal in the file system.
      private boolean is_open
      True when open.
      private long journal_number
      The journal number of this journal.
      private boolean read_only
      True if the journal file is read only.
      private int reference_count
      The number of threads currently looking at info in this journal.
      private java.util.HashMap resource_id_map
      A map between a resource name and an id for this journal file.

    • Constructor Summary

      Constructors 
      Constructor Description
      JournalFile​(java.io.File file, boolean read_only)
      Constructs the journal file.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      (package private) void addReference()
      Adds a reference preventing the journal file from being deleted.
      (package private) void buildPage​(long in_page_number, long position, byte[] buf, int off)
      Reconstructs a modification that is logged in this journal.
      (package private) void close()
      Closes the journal file.
      (package private) void closeAndDelete()
      Closes and deletes the journal file.
      (package private) void flushAndSynch()
      Synchronizes the log.
      (package private) long getJournalNumber()
      Returns the journal number assigned to this journal.
      (package private) boolean isDeleted()
      Returns true if the journal is deleted.
      (package private) JournalledSystem.JournalEntry logPageModification​(java.lang.String resource_name, long page_number, byte[] buf, int off, int len)
      Logs a page modification to the end of the log and returns a pointer in the file to the modification.
      (package private) void logResourceDelete​(java.lang.String resource_name)
      Logs that a resource was deleted.
      (package private) void logResourceSizeChange​(java.lang.String resource_name, long new_size)
      Logs a resource size change.
      (package private) void open​(long journal_number)
      Opens the journal file.
      (package private) JournalledSystem.JournalSummary openForRecovery()
      Opens the journal for recovery.
      (package private) void persist​(long start, long end)
      Plays the log from the given offset in the file to the next checkpoint.
      (package private) void removeReference()
      Removes a reference, if we are at the last reference the journal file is deleted.
      (package private) void setCheckPoint()
      Sets a check point.
      (package private) long size()
      Returns the size of the journal file in bytes.
      java.lang.String toString()  
      private java.lang.Long writeResourceName​(java.lang.String resource_name, java.io.DataOutputStream out)
      Writes a resource identifier to the stream for the resource with the given name.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Field Detail

      • file

        private java.io.File file
        The File object of this journal in the file system.

      • read_only

        private boolean read_only
        True if the journal file is read only.

      • data

        private StreamFile data
        The StreamFile object for reading and writing entries to/from the journal.

      • data_out

        private java.io.DataOutputStream data_out
        A DataOutputStream object used to write entries to the journal file.

      • buffer

        private byte[] buffer
        Small buffer.

      • resource_id_map

        private java.util.HashMap resource_id_map
        A map between a resource name and an id for this journal file.

      • cur_seq_id

        private long cur_seq_id
        The sequence id for resources modified in this log.

      • journal_number

        private long journal_number
        The journal number of this journal.

      • is_open

        private boolean is_open
        True when open.

      • reference_count

        private int reference_count
        The number of threads currently looking at info in this journal.

    • Constructor Detail

      • JournalFile

        public JournalFile​(java.io.File file,
                   boolean read_only)
        Constructs the journal file.

    • Method Detail

      • size

        long size()
        Returns the size of the journal file in bytes.

      • getJournalNumber

        long getJournalNumber()
        Returns the journal number assigned to this journal.

      • open

        void open​(long journal_number)
   throws java.io.IOException
        Opens the journal file. If the journal file exists then an error is generated.
        Throws:
        java.io.IOException

      • openForRecovery

        JournalledSystem.JournalSummary openForRecovery()
                                         throws java.io.IOException
        Opens the journal for recovery. This scans the journal and generates some statistics about the journal file such as the last check point and the journal number. If the journal file doesn't exist then an error is generated.
        Throws:
        java.io.IOException

      • close

        void close()
    throws java.io.IOException
        Closes the journal file.
        Throws:
        java.io.IOException

      • isDeleted

        boolean isDeleted()
        Returns true if the journal is deleted.

      • closeAndDelete

        void closeAndDelete()
             throws java.io.IOException
        Closes and deletes the journal file. This may not immediately close and delete the journal file if there are currently references to it (for example, in the middle of a read operation).
        Throws:
        java.io.IOException

      • addReference

        void addReference()
        Adds a reference preventing the journal file from being deleted.

      • removeReference

        void removeReference()
              throws java.io.IOException
        Removes a reference, if we are at the last reference the journal file is deleted.
        Throws:
        java.io.IOException

      • persist

        void persist​(long start,
             long end)
      throws java.io.IOException
        Plays the log from the given offset in the file to the next checkpoint. This will actually persist the log. Returns -1 if the end of the journal is reached.

        NOTE: This will not verify that the journal is correct. Verification should be done before the persist.

        Throws:
        java.io.IOException

      • writeResourceName

        private java.lang.Long writeResourceName​(java.lang.String resource_name,
                                         java.io.DataOutputStream out)
                                  throws java.io.IOException
        Writes a resource identifier to the stream for the resource with the given name.
        Throws:
        java.io.IOException

      • logResourceDelete

        void logResourceDelete​(java.lang.String resource_name)
                throws java.io.IOException
        Logs that a resource was deleted.
        Throws:
        java.io.IOException

      • logResourceSizeChange

        void logResourceSizeChange​(java.lang.String resource_name,
                           long new_size)
                    throws java.io.IOException
        Logs a resource size change.
        Throws:
        java.io.IOException

      • setCheckPoint

        void setCheckPoint()
            throws java.io.IOException
        Sets a check point. This will add an entry to the log.
        Throws:
        java.io.IOException

      • logPageModification

        JournalledSystem.JournalEntry logPageModification​(java.lang.String resource_name,
                                                  long page_number,
                                                  byte[] buf,
                                                  int off,
                                                  int len)
                                           throws java.io.IOException
        Logs a page modification to the end of the log and returns a pointer in the file to the modification.
        Throws:
        java.io.IOException

      • buildPage

        void buildPage​(long in_page_number,
               long position,
               byte[] buf,
               int off)
        throws java.io.IOException
        Reconstructs a modification that is logged in this journal.
        Throws:
        java.io.IOException

      • flushAndSynch

        void flushAndSynch()
            throws java.io.IOException
        Synchronizes the log.
        Throws:
        java.io.IOException

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object