Class STABLE

java.lang.Object
org.jgroups.stack.Protocol
org.jgroups.protocols.pbcast.STABLE

public class STABLE extends Protocol
Computes the broadcast messages that are stable; i.e., have been received by all members. Sends STABLE events up the stack when this is the case. This allows NAKACK to garbage collect messages that have been seen by all members.

Works as follows: periodically we mcast our highest seqnos (seen for each member) to the group. A stability vector, which maintains the highest seqno for each member and initially contains no data, is updated when such a message is received. The entry for a member P is computed set to min(entry[P], digest[P]). When messages from all members have been received, a stability message is mcast, which causes all members to send a STABLE event up the stack (triggering garbage collection in the NAKACK layer).

New: when max_bytes is exceeded (unless disabled by setting it to 0), a STABLE task will be started (unless it is already running). Design in docs/design/STABLE.txt

Version:
$Id: STABLE.java,v 1.85.2.3 2009/02/05 09:21:50 belaban Exp $
Author:
Bela Ban
  • Constructor Details

    • STABLE

      public STABLE()
  • Method Details

    • getName

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

      public long getDesiredAverageGossip()
    • setDesiredAverageGossip

      public void setDesiredAverageGossip(long gossip_interval)
    • getMaxBytes

      public long getMaxBytes()
    • setMaxBytes

      public void setMaxBytes(long max_bytes)
    • getBytes

      public long getBytes()
    • getStableSent

      public int getStableSent()
    • getStableReceived

      public int getStableReceived()
    • getStabilitySent

      public int getStabilitySent()
    • getStabilityReceived

      public int getStabilityReceived()
    • resetStats

      public void resetStats()
      Overrides:
      resetStats in class Protocol
    • requiredDownServices

      public Vector<Integer> requiredDownServices()
      Description copied from class: Protocol
      List of events that are required to be answered by some layer below.
      Overrides:
      requiredDownServices in class Protocol
      Returns:
      Vector (of Integers)
    • setProperties

      public boolean setProperties(Properties props)
      Description copied from class: Protocol
      Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:
       "loopback=false;unicast_inport=4444"
       
      Overrides:
      setProperties in class Protocol
    • start

      public void start() throws Exception
      Description copied from class: Protocol
      This method is called on a Channel.connect(String). Starts work. Protocols are connected and queues are ready to receive events. Will be called from bottom to top. This call will replace the START and START_OK events.
      Overrides:
      start in class Protocol
      Throws:
      Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception
    • stop

      public void stop()
      Description copied from class: Protocol
      This method is called on a Channel.disconnect(). Stops work (e.g. by closing multicast socket). Will be called from top to bottom. This means that at the time of the method invocation the neighbor protocol below is still working. This method will replace the STOP, STOP_OK, CLEANUP and CLEANUP_OK events. The ProtocolStack guarantees that when this method is called all messages in the down queue will have been flushed
      Overrides:
      stop in class Protocol
    • up

      public Object up(Event evt)
      Description copied from class: Protocol
      An event was received from the layer below. Usually the current layer will want to examine the event type and - depending on its type - perform some computation (e.g. removing headers from a MSG event type, or updating the internal membership list when receiving a VIEW_CHANGE event). Finally the event is either a) discarded, or b) an event is sent down the stack using down_prot.down() or c) the event (or another event) is sent up the stack using up_prot.up().
      Overrides:
      up in class Protocol
    • down

      public Object down(Event evt)
      Description copied from class: Protocol
      An event is to be sent down the stack. The layer may want to examine its type and perform some action on it, depending on the event's type. If the event is a message MSG, then the layer may need to add a header to it (or do nothing at all) before sending it down the stack using down_prot.down(). In case of a GET_ADDRESS event (which tries to retrieve the stack's address from one of the bottom layers), the layer may need to send a new response event back up the stack using up_prot.up().
      Overrides:
      down in class Protocol
    • runMessageGarbageCollection

      public void runMessageGarbageCollection()