org.jgroups.protocols

Class MERGE3

java.lang.Object

org.jgroups.stack.Protocol

org.jgroups.protocols.MERGE3

public class MERGE3
extends Protocol

Protocol to discover subgroups; e.g., existing due to a network partition (that healed). Example: group {p,q,r,s,t,u,v,w} is split into 3 subgroups {p,q}, {r,s,t,u} and {v,w}. This protocol will eventually send a MERGE event with the coordinators of each subgroup up the stack: {p,r,v}. Note that - depending on the time of subgroup discovery - there could also be 2 MERGE events, which first join 2 of the subgroups, and then the resulting group to the last subgroup. The real work of merging the subgroups into one larger group is done somewhere above this protocol (typically in the GMS protocol).

This protocol works as follows:

• If coordinator: periodically broadcast a "I'm the coordinator" message. If a coordinator receives such a message, it immediately initiates a merge by sending up a MERGE event

  Provides: sends MERGE event with list of coordinators up the stack
  

Author:

Bela Ban, Oct 16 2001

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MERGE3.CoordAnnouncement

Field Summary

Fields inherited from class org.jgroups.stack.Protocol

down_handler, down_prot, down_queue, down_thread, down_thread_prio, log, observer, props, stack, stats, up_handler, up_prot, up_queue, up_thread, up_thread_prio

Constructor Summary

Constructors

Constructor and Description
MERGE3()

Method Summary

Methods

Modifier and Type	Method and Description
void	down(Event evt) An event is to be sent down the stack.
java.lang.String	getName()
void	init() Called after instance has been created (null constructor) and before protocol is started.
boolean	setProperties(java.util.Properties props) Configures the protocol initially.
void	startDownHandler() This prevents the down-handler thread to be created, which is not needed in the protocol.
void	startUpHandler() This prevents the up-handler thread to be created, which is not needed in the protocol.
void	up(Event evt) An event was received from the layer below.

Methods inherited from class org.jgroups.stack.Protocol

destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, resetStats, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, start, statsEnabled, stop, stopInternal, upThreadEnabled

Methods inherited from class java.lang.Object

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

Constructor Detail

MERGE3

public MERGE3()

Method Detail

getName

public java.lang.String getName()

Specified by:

getName in class Protocol

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

init

public void init()
          throws java.lang.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:

java.lang.Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception

startUpHandler

public void startUpHandler()

This prevents the up-handler thread to be created, which is not needed in the protocol. DON'T REMOVE !

Overrides:

startUpHandler in class Protocol

startDownHandler

public void startDownHandler()

This prevents the down-handler thread to be created, which is not needed in the protocol. DON'T REMOVE !

Overrides:

startDownHandler in class Protocol

up

public void 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 passDown() or c) the event (or another event) is sent up the stack using passUp().

Overrides:

up in class Protocol

down

public void 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 passDown(). 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 passUp().

Overrides:

down in class Protocol