Class FRAG

java.lang.Object
org.jgroups.stack.Protocol
org.jgroups.protocols.FRAG
public class FRAG extends Protocol
Fragmentation layer. Fragments messages larger than FRAG_SIZE into smaller packets. Reassembles fragmented packets into bigger ones. The fragmentation number is prepended to the messages as a header (and removed at the receiving side).

Each fragment is identified by (a) the sender (part of the message to which the header is appended), (b) the fragmentation ID (which is unique per FRAG layer (monotonically increasing) and (c) the fragement ID which ranges from 0 to number_of_fragments-1.

Requirement: lossless delivery (e.g. NAK, ACK). No requirement on ordering. Works for both unicast and multicast messages.

Version:
$Id: FRAG.java,v 1.39.2.2 2008/07/22 14:08:59 belaban Exp $
Author:
Bela Ban, Filip Hanik

  • Constructor Details

    • FRAG

      public FRAG()

  • Method Details

    • getName

      public String getName()
      Specified by:
      getName in class Protocol

    • getFragSize

      public int getFragSize()

    • setFragSize

      public void setFragSize(int s)

    • getNumberOfSentMessages

      public long getNumberOfSentMessages()

    • getNumberOfSentFragments

      public long getNumberOfSentFragments()

    • getNumberOfReceivedMessages

      public long getNumberOfReceivedMessages()

    • getNumberOfReceivedFragments

      public long getNumberOfReceivedFragments()

    • setProperties

      public boolean setProperties(Properties props)
      Setup the Protocol instance acording to the configuration string
      Overrides:
      setProperties in class Protocol

    • init

      public void init() throws Exception
      Description copied from class: Protocol
      Called after instance has been created (null constructor) and before protocol is started. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.
      Overrides:
      init in class Protocol
      Throws:
      Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception

    • resetStats

      public void resetStats()
      Overrides:
      resetStats in class Protocol

    • down

      public Object down(Event evt)
      Fragment a packet if larger than frag_size (add a header). Otherwise just pass down. Only add a header if framentation is needed !
      Overrides:
      down in class Protocol

    • up

      public Object up(Event evt)
      If event is a message, if it is fragmented, re-assemble fragments into big message and pass up the stack.
      Overrides:
      up in class Protocol