org.javagroups.demos
Class QuoteServer

java.lang.Object
  |
  +--org.javagroups.demos.QuoteServer

All Implemented Interfaces:

MembershipListener, MessageListener

public class QuoteServer

extends java.lang.Object

implements MembershipListener, MessageListener

Example of a replicated quote server. The server maintains state which consists of a list of quotes and their corresponding values. When it is started, it tries to reach other quote servers to get its initial state. If it does not receive any response after 5 seconds, it assumes it is the first server and starts processing requests. When it receives a view notification it checks whether there are more members in the view than in its previous view. If this is the case, it broadcasts a request for the state to all members. Integration of different states is simply the union of all states (with the danger of overwriting mutually inconsistent state).

This mechanism allows both for fast discovery of initial servers, and - in the case of partition merging - for reintegration of existing servers. Broadcasting the state request upon every view change (only when new members are joined) causes potentially a lot of network traffic, but it is assumes that there will not be more than 5 quote servers at most.

Author:

Bela Ban

Constructor Summary

QuoteServer()

Method Summary

void	block() Block sending and receiving of messages until viewAccepted() is called
java.util.Hashtable	getAllStocks()
float	getQuote(java.lang.String stock_name)
byte[]	getState()
static void	main(java.lang.String[] args)
void	printAllStocks()
void	receive(Message msg)
void	setQuote(java.lang.String stock_name, java.lang.Float value)
void	setState(byte[] state)
void	start()
void	suspect(Address suspected_mbr) Called when a member is suspected
void	viewAccepted(View new_view) Called by JavaGroups to notify the target object of a change of membership.

Methods inherited from class java.lang.Object

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

Constructor Detail

QuoteServer

public QuoteServer()

Method Detail

viewAccepted

public void viewAccepted(View new_view)

Description copied from interface: MembershipListener

Called by JavaGroups to notify the target object of a change of membership. No long running actions should be done in this callback in the case of Ensemble, as this would block Ensemble. If some long running action needs to be performed, it should be done in a separate thread (cf. ../Tests/QuoteServer.java).

Specified by:

viewAccepted in interface MembershipListener

suspect

public void suspect(Address suspected_mbr)

Description copied from interface: MembershipListener

Called when a member is suspected

Specified by:

suspect in interface MembershipListener

block

public void block()

Description copied from interface: MembershipListener

Block sending and receiving of messages until viewAccepted() is called

Specified by:

block in interface MembershipListener

start

public void start()

getQuote

public float getQuote(java.lang.String stock_name)
               throws java.lang.Exception

java.lang.Exception

setQuote

public void setQuote(java.lang.String stock_name,
                     java.lang.Float value)

getAllStocks

public java.util.Hashtable getAllStocks()

printAllStocks

public void printAllStocks()

receive

public void receive(Message msg)

Specified by:

receive in interface MessageListener

getState

public byte[] getState()

Specified by:

getState in interface MessageListener

setState

public void setState(byte[] state)

Specified by:

setState in interface MessageListener

main

public static void main(java.lang.String[] args)