org.jgroups.protocols

Class MERGE2

java.lang.Object

org.jgroups.stack.Protocol

org.jgroups.protocols.MERGE2

public class MERGE2
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 retrieve the initial membership (using the FIND_INITIAL_MBRS event provided e.g. by PING or TCPPING protocols. This list contains {coord,addr} pairs.
• If there is more than 1 coordinator:
  1. Get all coordinators
  2. Create a MERGE event with the list of coordinators as argument
  3. Send the event up the stack

Requires: FIND_INITIAL_MBRS event from below
Provides: sends MERGE event with list of coordinators up the stack

Author:

Bela Ban, Oct 16 2001

Field Summary

Fields inherited from class org.jgroups.stack.Protocol

down_prot, log, props, stack, stats, up_prot

Constructor Summary

Constructors

Constructor and Description
MERGE2()

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.Object	down(Event evt) An event is to be sent down the stack.
long	getMaxInterval()
long	getMinInterval()
java.lang.String	getName()
boolean	getSuspended()
void	init() Called after instance has been created (null constructor) and before protocol is started.
java.util.Vector<java.lang.Integer>	requiredDownServices() List of events that are required to be answered by some layer below.
void	resumeMergeTask() Resumes the sending of merge multicast (only if coord)
void	sendMergeSolicitation() Discovers members and detects whether we have multiple coordinator.
void	setMaxInterval(long l)
void	setMinInterval(long i)
boolean	setProperties(java.util.Properties props) Configures the protocol initially.
void	stop() This method is called on a Channel.disconnect().
void	suspendMergeTask() Suspends the sending of merge multicasts (only if coord)
java.lang.Object	up(Event evt) An event was received from the layer below.

Methods inherited from class org.jgroups.stack.Protocol

destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getProperties, getProtocolStack, getThreadFactory, getTransport, getUpProtocol, printStats, providedDownServices, providedUpServices, requiredUpServices, resetStats, setDownProtocol, setPropertiesInternal, setProtocolStack, setUpProtocol, start, statsEnabled, upThreadEnabled

Methods inherited from class java.lang.Object

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

Constructor Detail

MERGE2

public MERGE2()

Method Detail

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

getName

public java.lang.String getName()

Specified by:

getName in class Protocol

getMinInterval

public long getMinInterval()

setMinInterval

public void setMinInterval(long i)

getMaxInterval

public long getMaxInterval()

setMaxInterval

public void setMaxInterval(long l)

getSuspended

public boolean getSuspended()

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

requiredDownServices

public java.util.Vector<java.lang.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)

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 java.lang.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 java.lang.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

suspendMergeTask

public void suspendMergeTask()

Suspends the sending of merge multicasts (only if coord)

resumeMergeTask

public void resumeMergeTask()

Resumes the sending of merge multicast (only if coord)

sendMergeSolicitation

public void sendMergeSolicitation()

Discovers members and detects whether we have multiple coordinator. If so, kicks off a merge