org.jgroups.protocols

Class GMS

java.lang.Object

org.jgroups.stack.Protocol

org.jgroups.stack.MessageProtocol

org.jgroups.stack.RpcProtocol

org.jgroups.protocols.GMS

All Implemented Interfaces:

java.lang.Runnable, RequestHandler

public class GMS
extends RpcProtocol
implements java.lang.Runnable

Group membership protocol. Handles joins/leaves/crashes (suspicions) and emits new views accordingly. Use VIEW_ENFORCER on top of this layer to make sure new members don't receive any messages until they are members.

Author:

Bela Ban

Field Summary

Fields

Modifier and Type	Field and Description
java.lang.String	group_addr
java.lang.Object	impl_mutex
long	join_retry_timeout
long	join_timeout
long	leave_timeout
Address	local_addr
long	ltime
Membership	mbrs
static java.lang.String	name
ViewId	view_id
java.lang.Object	view_mutex

Fields inherited from class org.jgroups.stack.MessageProtocol

_corr, members

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
GMS()

Method Summary

Methods

Modifier and Type	Method and Description
void	becomeClient()
void	becomeCoordinator()
void	becomeParticipant()
void	castViewChange(java.util.Vector new_mbrs, java.util.Vector old_mbrs, java.util.Vector suspected_mbrs) Compute a new view, given the current view, the new members and the suspected/left members.
protected boolean	checkSelfInclusion(java.util.Vector mbrs) Returns true if local_addr is member of mbrs, else false
protected Address	determineCoordinator()
void	flush(java.util.Vector flush_dest, java.util.Vector suspected_mbrs) FLUSH protocol.
java.lang.String	getName()
View	getNextView(java.util.Vector new_mbrs, java.util.Vector old_mbrs, java.util.Vector suspected_mbrs) Computes the next view.
boolean	handleDownEvent(Event evt) Callback.
boolean	handleJoin(Address mbr)
void	handleLeave(Address mbr, boolean suspected)
View	handleMerge(ViewId other_vid, java.util.Vector other_members)
void	handleSuspect(Address mbr)
boolean	handleUpEvent(Event evt) Callback.
void	handleViewChange(ViewId new_view, java.util.Vector mbrs)
void	installView(ViewId new_view, java.util.Vector mbrs) Assigns the new ltime.
void	join(Address mbr)
void	leave(Address mbr)
View	makeView(java.util.Vector mbrs)
static View	makeView(java.util.Vector mbrs, ViewId vid)
void	merge(java.util.Vector other_coords)
void	receiveDownEvent(Event evt) Internal method, should not be called by clients.
java.util.Vector	requiredDownServices() List of events that are required to be answered by some layer below.
void	run()
void	setImpl(GmsImpl new_impl)
boolean	setProperties(java.util.Properties props) Setup the Protocol instance acording to the configuration string
void	start() This method is called on a Channel.connect(String).
void	suspect(Address mbr)

Methods inherited from class org.jgroups.stack.RpcProtocol

callRemoteMethod, callRemoteMethod, callRemoteMethod, callRemoteMethod, callRemoteMethods, callRemoteMethods, callRemoteMethods, handle

Methods inherited from class org.jgroups.stack.MessageProtocol

castMessage, down, sendMessage, stop, up, updateView

Methods inherited from class org.jgroups.stack.Protocol

destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, passDown, passUp, printStats, providedDownServices, providedUpServices, receiveUpEvent, requiredUpServices, resetStats, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, startDownHandler, startUpHandler, statsEnabled, stopInternal, upThreadEnabled

Methods inherited from class java.lang.Object

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

Field Detail

local_addr

public Address local_addr

group_addr

public java.lang.String group_addr

mbrs

public final Membership mbrs

view_id

public ViewId view_id

ltime

public long ltime

join_timeout

public long join_timeout

join_retry_timeout

public long join_retry_timeout

leave_timeout

public long leave_timeout

impl_mutex

public final java.lang.Object impl_mutex

view_mutex

public final java.lang.Object view_mutex

name

public static final java.lang.String name

See Also:

Constant Field Values

Constructor Detail

GMS

public GMS()

Method Detail

getName

public java.lang.String getName()

Overrides:

getName in class RpcProtocol

requiredDownServices

public java.util.Vector 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)

setImpl

public void setImpl(GmsImpl new_impl)

start

public void start()
           throws java.lang.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 MessageProtocol

Throws:

java.lang.Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception

becomeCoordinator

public void becomeCoordinator()

becomeParticipant

public void becomeParticipant()

becomeClient

public void becomeClient()

getNextView

public View getNextView(java.util.Vector new_mbrs,
               java.util.Vector old_mbrs,
               java.util.Vector suspected_mbrs)

Computes the next view. Returns a copy that has old_mbrs and suspected_mbrs removed and new_mbrs added.

flush

public void flush(java.util.Vector flush_dest,
         java.util.Vector suspected_mbrs)

FLUSH protocol. Send to current mbrs - suspected_mbrs (not including new_mbrs, but including old_mbr) Send TMP_VIEW event down, this allows FLUSH/NAKACK to set membership correctly

castViewChange

public void castViewChange(java.util.Vector new_mbrs,
                  java.util.Vector old_mbrs,
                  java.util.Vector suspected_mbrs)

Compute a new view, given the current view, the new members and the suspected/left members. Run view update protocol to install a new view in all members (this involves casting the new view to all members). The targets for FLUSH and VIEW mcasts are computed as follows:

 existing          leaving        suspected          joining
 

 1. FLUSH         y                 y               n                 n
 2. new_view      y                 n               n                 y
 3. tmp_view      y                 y               n                 y
 (view_dest)
 

1. The FLUSH is only sent to the existing and leaving members (they are the only ones that might have old messages not yet seen by the group. The suspected members would not answer anyway (because they have failed) and the joining members have certainly no old messages.
2. The new view to be installed includes the existing members plus the joining ones and excludes the leaving and suspected members.
3. A temporary view is sent down the stack as an event. This allows the bottom layer (e.g. UDP or TCP) to determine the members to which to send a multicast message. Compared to the new view, leaving members are included since they have are waiting for a view in which they are not members any longer before they leave. So, if we did not set a temporary view, joining members would not receive the view (signalling that they have been joined successfully). The temporary view is essentially the current view plus the joining members (old members are still part of the current view).

installView

public void installView(ViewId new_view,
               java.util.Vector mbrs)

Assigns the new ltime. Installs view and view_id. Changes role to coordinator if necessary. Sends VIEW_CHANGE event up and down the stack.

determineCoordinator

protected Address determineCoordinator()

checkSelfInclusion

protected boolean checkSelfInclusion(java.util.Vector mbrs)

Returns true if local_addr is member of mbrs, else false

makeView

public View makeView(java.util.Vector mbrs)

makeView

public static View makeView(java.util.Vector mbrs,
            ViewId vid)

join

public void join(Address mbr)

leave

public void leave(Address mbr)

suspect

public void suspect(Address mbr)

merge

public void merge(java.util.Vector other_coords)

handleJoin

public boolean handleJoin(Address mbr)

handleLeave

public void handleLeave(Address mbr,
               boolean suspected)

handleViewChange

public void handleViewChange(ViewId new_view,
                    java.util.Vector mbrs)

handleMerge

public View handleMerge(ViewId other_vid,
               java.util.Vector other_members)

handleSuspect

public void handleSuspect(Address mbr)

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.

receiveDownEvent

public void receiveDownEvent(Event evt)

Description copied from class: Protocol

Internal method, should not be called by clients. Used by ProtocolStack. I would have used the 'friends' modifier, but this is available only in C++ ... If the down_handler thread is not available (down_thread == false), then directly call the down() method: we will run on the caller's thread (e.g. the protocol layer above us).

Overrides:

receiveDownEvent in class Protocol

setProperties

public boolean setProperties(java.util.Properties props)

Setup the Protocol instance acording to the configuration string

Overrides:

setProperties in class Protocol

run

public void run()

Specified by:

run in interface java.lang.Runnable