Package org.jgroups.util

Class RetransmitTable

java.lang.Object
org.jgroups.util.RetransmitTable
public class RetransmitTable extends Object
A store for messages to be retransmitted or delivered. Used on sender and receiver side, as a replacement for HashMap. RetransmitTable should use less memory than HashMap, as HashMap.Entry has 4 fields, plus arrays for storage.

RetransmitTable maintains a matrix (an array of arrays) of messages. Messages are stored in the matrix by mapping their seqno to an index. E.g. when we have 10 rows of 1000 messages each, and first_seqno is 3000, then a message with seqno=5600, will be stored in the 3rd row, at index 600.

Rows are removed when all messages in that row have been received.

This class in not synchronized; the caller has to make sure access to it is synchronized

Author:
Bela Ban

  • Field Details

    • num_rows

      protected final int num_rows

    • msgs_per_row

      protected final int msgs_per_row

    • resize_factor

      protected final double resize_factor

    • matrix

      protected Message[][] matrix

    • offset

      protected long offset
      The first seqno, at matrix[0][0]

    • size

      protected int size

    • highest_seqno_purged

      protected long highest_seqno_purged
      The highest seqno purged

    • highest_seqno

      protected long highest_seqno
      The highest seqno in the table

    • max_compaction_time

      protected long max_compaction_time
      Time (in ms) after which a compaction should take place. 0 disables compaction

    • last_compaction_timestamp

      protected long last_compaction_timestamp
      The time when the last compaction took place. If a compact() takes place and sees that the last compaction is more than max_compaction_time ms ago, a compaction will take place

    • automatic_purging

      protected boolean automatic_purging
      By default, rows are only nulled and highest_seqno_purged is adjusted when purge(long) is called. When automatic_purging is enabled (default is off), rows are purged and highest_seqno_purged is adjusted on remove(long)

    • DEFAULT_MAX_COMPACTION_TIME

      protected static final long DEFAULT_MAX_COMPACTION_TIME
      See Also:

    • DEFAULT_RESIZE_FACTOR

      protected static final double DEFAULT_RESIZE_FACTOR
      See Also:

    • log

      protected static final Log log

  • Constructor Details

    • RetransmitTable

      public RetransmitTable()

    • RetransmitTable

      public RetransmitTable(int num_rows, int msgs_per_row, long offset)

    • RetransmitTable

      public RetransmitTable(int num_rows, int msgs_per_row, long offset, double resize_factor)

    • RetransmitTable

      public RetransmitTable(int num_rows, int msgs_per_row, long offset, double resize_factor, long max_compaction_time, boolean automatic_purging)

  • Method Details

    • getOffset

      public long getOffset()

    • capacity

      public int capacity()
      Returns the total capacity in the matrix

    • size

      public int size()
      Returns the numbers of messages in the table

    • isEmpty

      public boolean isEmpty()

    • getHighest

      public long getHighest()

    • getHighestPurged

      public long getHighestPurged()

    • getMaxCompactionTime

      public long getMaxCompactionTime()

    • setMaxCompactionTime

      public void setMaxCompactionTime(long max_compaction_time)

    • isAutomaticPurging

      public boolean isAutomaticPurging()

    • setAutomaticPurging

      public void setAutomaticPurging(boolean automatic_purging)

    • getFillFactor

      public double getFillFactor()
      Returns the ratio between size and capacity, as a percentage

    • put

      public boolean put(long seqno, Message msg)
      Adds a new message to the index computed as a function of seqno
      Parameters:
      seqno -
      msg -
      Returns:
      True if the element at the computed index was null, else false

    • putIfAbsent

      public Message putIfAbsent(long seqno, Message msg)
      Adds a message if the element at the given index is null. Returns null if no message existed at the given index, else returns the existing message and doesn't set the element.
      Parameters:
      seqno -
      msg -
      Returns:
      The existing message, or null if there wasn't any

    • get

      public Message get(long seqno)

    • get

      public List<Message> get(long from, long to)

    • remove

      public Message remove(long seqno)
      Removes the message with seqno from the table, nulls the index

    • clear

      public void clear()
      Removes all elements. This method is usually called just before removing a retransmit table, so typically it is not used anymore after returning

    • purge

      public void purge(long seqno)
      Removes all messages less than or equal to seqno from the table. Does this by nulling entire rows in the matrix and nulling all elements invalid input: '<' index(seqno) of the first row that cannot be removed
      Parameters:
      seqno -

    • resize

      protected void resize(long seqno)
      Moves rows down the matrix, by removing purged rows. If resizing to accommodate seqno is still needed, computes a new size. Then either moves existing rows down, or copies them into a new array (if resizing took place)

    • move

      protected void move(int num_rows)
      Moves contents of matrix num_rows down. Avoids a System.arraycopy()

    • compact

      public void compact()
      Moves the contents of matrix down by the number of purged rows and resizes the matrix accordingly. The capacity of the matrix should be size * resize_factor

    • computeSize

      public int computeSize()
      Iterate from highest_seqno_purged to highest_seqno and add up non-null values

    • getNullMessages

      public int getNullMessages(long to)
      Returns the number of null elements up to 'to'

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • dump

      public String dump()
      Dumps the seqnos in the table as a list

    • dumpMatrix

      public String dumpMatrix()
      Dumps the non-null in the table in a pseudo graphic way

    • getRow

      protected Message[] getRow(int index)
      Returns a row. Creates a new row and inserts it at index if the row at index doesn't exist
      Parameters:
      index -
      Returns:
      A row

    • computeRow

      protected int computeRow(long seqno)
      Computes and returns the row index for seqno

    • computeIndex

      protected int computeIndex(long seqno)
      Computes and returns the index within a row for seqno