JavaGroups.JavaStack.Protocols
Class STABLE

java.lang.Object
  |
  +--JavaGroups.JavaStack.Protocol
        |
        +--JavaGroups.JavaStack.MessageProtocol
              |
              +--JavaGroups.JavaStack.RpcProtocol
                    |
                    +--JavaGroups.JavaStack.Protocols.STABLE

public class STABLE

extends RpcProtocol

implements java.lang.Runnable

Computes the broadcast messages that are stable, i.e. have been received by all members. Sends STABLE events up te stack when this is the case. Uses a probabilistic scheme to do so, as described in "GSGC: An Efficient Gossip-Style Garbage Collection Scheme for Scalable Reliable Multicast".

The only difference is that instead of using counters for an estimation of messages received from each member, we retrieve this actual information from the NAKACK layer (which must be present for the STABLE protocol to work).

Constructor Summary

STABLE()

Method Summary

java.lang.String	GetName()
void	Gossip(ViewId view_id, long round, long[] highest_seqnos, boolean[] heard, java.lang.Object sender) Contains the highest sequence numbers as seen by sender
boolean	HandleDownEvent(Event evt) Callback.
boolean	HandleUpEvent(Event evt) Callback.
java.util.Vector	RequiredUpServices() List of events that are required to be answered by some layer above.
void	run()
boolean	SetProperties(java.util.Properties props) Configures the protocol initially.
void	Stability(ViewId view_id, long round, long[] stability_vector, java.lang.Object sender) Contains the highest message sequence numbers (for each member) that can safely be deleted (because they have been seen by all members).

Methods inherited from class JavaGroups.JavaStack.RpcProtocol

CallRemoteMethod, CallRemoteMethod, CallRemoteMethod, CallRemoteMethod, CallRemoteMethod, CallRemoteMethod, CallRemoteMethod, CallRemoteMethods, CallRemoteMethods, CallRemoteMethods, CallRemoteMethods, CallRemoteMethods, CallRemoteMethods, CallRemoteMethods, Handle

Methods inherited from class JavaGroups.JavaStack.MessageProtocol

CastMessage, Down, SendMessage, Up

Methods inherited from class JavaGroups.JavaStack.Protocol

GetDownProtocol, GetProperties, GetUpProtocol, PassDown, PassUp, ProvidedDownServices, ProvidedUpServices, RequiredDownServices, Reset, SetDownProtocol, SetProtocolStack, SetUpProtocol, StartDownHandler, StartUpHandler, StopInternal

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

STABLE

public STABLE()

Method Detail

GetName

public java.lang.String GetName()

Overrides:

GetName in class RpcProtocol

RequiredUpServices

public java.util.Vector RequiredUpServices()

Description copied from class: Protocol

List of events that are required to be answered by some layer above.

Overrides:

RequiredUpServices in class Protocol

Tags copied from class: Protocol

Returns:

Vector (of Integers)

SetProperties

public boolean SetProperties(java.util.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

Gossip

public void Gossip(ViewId view_id,
                   long round,
                   long[] highest_seqnos,
                   boolean[] heard,
                   java.lang.Object sender)

Contains the highest sequence numbers as seen by sender

Parameters:

view_id - The view ID in which the gossip was sent. Must be the same as ours, otherwise it is discarded

round - The round in which the gossip was sent

highest_seqnos - A vector with the highest sequence numbers as seen bu sender

heard - The sender's heard_from array. This allows us to minimize the gossip msgs for a given round as a member does not have to receive gossip msgs from each member, but members pass gossips they've received from others on in their own gossips. E.g. when a member P (of group {P,Q,R}) receives a gossip from R, its own gossip to Q might be {R,P}. Q, who hasn't received a gossip from R, will not need to receive it anymore as it is already sent by P. This simple scheme reduces the number of gossip messages needed.

sender - The sender of the gossip message (obviously :-))

Stability

public void Stability(ViewId view_id,
                      long round,
                      long[] stability_vector,
                      java.lang.Object sender)

Contains the highest message sequence numbers (for each member) that can safely be deleted (because they have been seen by all members).

HandleUpEvent

public boolean HandleUpEvent(Event evt)

Callback. Called by superclass when event may be handled.

Do not use PassUp in this method as the event is passed up by default by the superclass after this method returns !

Overrides:

HandleUpEvent in class RpcProtocol

Returns:

boolean Defaults to true. If false, event will not be passed up the stack.

HandleDownEvent

public boolean HandleDownEvent(Event evt)

Callback. Called by superclass when event may be handled.

Do not use PassDown in this method as the event is passed down by default by the superclass after this method returns !

Overrides:

HandleDownEvent in class RpcProtocol

Returns:

boolean Defaults to true. If false, event will not be passed down the stack.

run

public void run()

Specified by:

run in interface java.lang.Runnable